Metal alloys for the reflective or the semi-reflective layer of an optical storage medium

ABSTRACT

A silver-based magnesium alloy thin film is provided for the semi-reflective coating layer of optical discs. This alloy has moderate to high reflectivity and reasonable corrosion resistance in the ambient environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/506,548, filed Apr. 27, 2012, now U.S. Pat. No. 8,632,869, which is acontinuation of U.S. patent application Ser. No. 12/460,831, filed Jul.24, 2009, which is a continuation of U.S. patent application Ser. No.11/390,776, filed Mar. 28, 2006, now U.S. Pat. No. 7,645,500, which is acontinuation of U.S. patent application Ser. No. 10/825,779, filed Apr.16, 2004, now U.S. Pat. No. 7,018,696, which claims the benefit of U.S.Provisional Application No. 60/463,837 filed Apr. 18, 2003. Theseapplications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to reflective layers or semi-reflective layersused in optical storage media that comprise silver-based alloys.

BACKGROUND OF THE INVENTION

Four layers are generally present in the construction of a conventional,prerecorded, optical disc such as compact audio disc. A first layer isusually made from optical grade, polycarbonate resin. This layer ismanufactured by well-known techniques that usually begin by injection orcompression molding the resin into a disc. The surface of the disc ismolded or stamped with extremely small and precisely located pits andlands. These pits and lands have a predetermined size and, as explainedbelow, are ultimately the vehicles for storing information on the disc.

After stamping, an optically reflective layer is placed over theinformation pits and lands. The reflective layer is usually made ofaluminum or an aluminum alloy and is typically between about 40 to about100 nanometers (nm) thick. The reflective layer is usually deposited byone of many well-known vapor deposition techniques such as sputtering orthermal evaporation. Kirk-Othmer, Encyclopedia of Chemical Technology,3^(rd) ed. Vol. 10, pp. 247 to 283, offers a detailed explanation ofthese and other deposition techniques such as glow discharge, ionplating, and chemical vapor deposition, and this specification herebyincorporates that disclosure by reference.

Next, a solvent-based or an UV (ultraviolet) curing-type resin isapplied over the reflective layer, which is usually followed by a label.The third layer protects the reflective layer from handling and theambient environment. And the label identifies the particular informationthat is stored on the disc, and sometimes, may include artwork.

The information pits residing between the polycarbonate resin and thereflective layer usually take the form of a continuous spiral. Thespiral typically begins at an inside radius and ends at an outsideradius. The distance between any 2 spirals is called the “track pitch”and is usually about 1.6 microns for compact audio disc. The length ofone pit or land in the direction of the track is from about 0.9 to about3.3 microns. All of these details are commonly known for compact audiodiscs and reside in a series of specifications that were first proposedby Philips NV of Holland and Sony of Japan as standards for theindustry.

The disc is read by pointing a laser beam through the optical gradepolycarbonate substrate and onto the reflective layer with sufficientlysmall resolution to focus on the information pits. The pits have a depthof about ¼of the wavelength of the laser light, and the light generallyhas a wavelength in the range of about 780 to 820 nanometers.Destructive (dark) or constructive (bright) interference of the laserlight is then produced as the laser travels along the spiral track,focusing on an alternating stream of pits and lands in its path.

This on and off change of light intensity from dark to bright or frombright to dark forms the basis of a digital data stream of 1 and 0's.When there is no light intensity change in a fixed time interval, thedigital signal is “0,” and when there is light intensity change fromeither dark to bright or bright to dark, the digital signal is “1.” Thecontinuous stream of ones and zeros that results is then electronicallydecoded and presented in a format that is meaningful to the user such asmusic or computer programming data.

As a result, it is important to have a highly reflective coating on thedisc to reflect the laser light from the disc and onto a detector inorder to read the presence of an intensity change. In general, thereflective layer is usually aluminum, copper, silver, or gold, all ofwhich have a high optical reflectivity of more than 80 percent from 650nm to 820 nm wavelength. Aluminum and aluminum alloys are commonly usedbecause they have a comparatively lower cost, adequate corrosionresistance, and are easily placed onto the polycarbonate disc.

Occasionally and usually for cosmetic reason, a gold or copper basedalloy is used to offer the consumer a “gold” colored disc. Although goldnaturally offers a rich color and satisfies all the functionalrequirements of a highly reflective layer, it is comparatively much moreexpensive than aluminum. Therefore, a copper-based alloy that containszinc or tin is sometimes used to produce the gold colored layer. Butunfortunately, the exchange is not truly satisfactory because the copperalloy's corrosion resistance, in general, is considered worse thanaluminum, which results in a disc that has a shorter life span than onewith an aluminum reflective layer.

For the convenience of the reader, additional details in the manufactureand operation of an optically readable storage system can be found inU.S. Pat. No. 4,998,239 to Strandjord et al. and U.S. Pat. No. 4,709,363to Dirks et al., the disclosures of which are hereby incorporated byreference.

Another type of disc in the compact disc family that has become popularis the recordable compact disc or “CD-R.” This disc is similar to the CDdescribed earlier, but it has a few changes. The recordable compact discbegins with a continuous spiral groove instead of a continuous spiral ofpits and has a layer of organic dye between the polycarbonate substrateand the reflective layer. The disc is recorded by periodically focusinga laser beam into the grooves as the laser travels along the spiraltrack. The laser heats the dye to a high temperature, which in turnplaces pits in the groove that coincide with an input data stream ofones and zeros by periodically deforming and decomposing the dye.

For the convenience of the reader, additional details regarding theoperation and construction of these recordable discs can be found inU.S. Pat. No. 5,325,351 to Uchiyama et al., and U.S. Pat. Nos.5,391,462; 5,415,914; and 5,419,939 to Arioka et al., and U.S. Pat. No.5,620,767 to Harigaya et al., the disclosures of which are herebyincorporated into this specification by reference.

The key component of a CD-R disc is the organic dye, which is made fromsolvent and one or more organic compounds from the cyanine,phthalocyanine or azo family. The disc is normally produced by spincoating the dye onto the disc and sputtering the reflective layer overthe dye after the dye is sufficiently dry. But because the dye maycontain halogen ions or other chemicals that can corrode the reflectivelayer, many commonly used reflective layer material's such as aluminummay not be suitable to give the CD-R disc a reasonable life span. Sobeing, frequently gold must be used to manufacture a recordable CD. Butwhile gold satisfies all the functional requirements of CD-R discs, itis a very expensive solution.

Recently, other types of recordable optical disks have been developed.These optical disks use a phase-change or magneto-optic material as therecording medium. An optical laser is used to change the phase ormagnetic state (microstructural change) of the recording layer bymodulating a beam focused on the recording medium while the medium isrotated to produce microstructural changes in the recording layer.During playback, changes in the intensity of light from the optical beamreflected through the recording medium are sensed by a detector. Thesemodulations in light intensity are due to variations in themicrostructure of the recording medium produced during the recordingprocess. Some phase-change and/or magneto-optic materials may be readilyand repeatedly transformed from a first state to a second state and backagain with substantially no degradation. These materials may be used asthe recording media for a compact disc-rewritable disc, or commonlyknown as CD-RW.

To record and read information, phase change discs utilize the recordinglayer's ability to change from a first dark to a second light phase andback again. Recording on these materials produces a series ofalternating dark and light spots according to digital input dataintroduced as modulations in the recording laser beam. These light anddark spots on the recording medium correspond to 0's and 1's in terms ofdigital data. The digitized data is read using a low laser power focusedalong the track of the disc to play back the recorded information. Thelaser power is low enough such that it does not further change the stateof the recording media but is powerful enough such that the variationsin reflectivity of the recording medium may be easily distinguished by adetector. The recording medium may be erased for re-recording byfocussing a laser of intermediate power on the recording medium. Thisreturns the recording medium layer to its original or erased state. Amore detailed discussion of the recording mechanism of opticallyrecordable media can be found in U.S. Pat. Nos. 5,741,603; 5,498,507;and 5,719,006 assigned to the Sony Corporation, the TDK Corporation, andthe NEC Corporation, all of Tokyo, Japan, respectively, the disclosuresof which are incorporated herein by reference in their entirety.

Still another type of disc in the optical disc family that has becomepopular is a prerecorded optical disc called the digital videodisc or“DVD.” This disc has two halves. Each half is made of polycarbonateresin that has been injection or compression molded with pit informationand then sputter coated with a reflective layer, as described earlier.These two halves are then bonded or glued together with an UV curingresin or a hot melt adhesive to form the whole disc. The disc can thenbe played from both sides as contrasted from the compact disc or CDwhere information is usually obtained only from one side. The size of aDVD is about the same as a CD, but the information density isconsiderably higher. The track pitch is about 0.7 micron and the lengthof the pits and lands is from approximately 0.3 to 1.4 microns.

One variation of the DVD family of discs is the DVD-dual layer disc.This disc also has two information layers; however, both layers areplayed back from one side. In this arrangement, the highly reflectivelayer is usually the same as that previously described. But the secondlayer is only semi-reflective with a reflectivity in the range ofapproximately 18 to 30 percent at 650 nm wavelength. In addition toreflecting light, this second layer must also pass a substantial amountof light so that the laser beam can reach the highly reflective layerunderneath and then reflect back through the semi-reflective layer tothe signal detector.

In a continued attempt to increase the storage capacity of opticaldiscs, a multi-layer disc can be constructed as indicated in thepublication “SPIE Conference Proceeding Vol. 2890, page 2-9, November,1996” where a tri-layer or a quadri-layer optical disc was revealed. Allthe data layers were played back from one side of the disc using laserlight at 650 nm wavelength. A double-sided tri-layered read-only-discthat included a total of six layers can have a storage capacity of about26 gigabytes of information.

More recently, a blue light emitting laser diode with wavelength of 400nm has been made commercially available. The new laser will enable muchdenser digital videodisc data storage. While current DVD using 650 nmred laser can store 4.7 GB per side, the new blue laser will enable 12GB per side, enough storage space for about 6 hours ofstandard-resolution video and sound. With a multi-layer disc, there isenough capacity for a featured movie in the high-definition digitalvideo format.

Recent advances in the development of high reflective andsemi-reflective materials for use as both semi-reflective and highlyreflective layers in DVD-9s has made it feasible to create tri-layer andeven quadruple-layer optical discs with all playback information layerson the same side of the disc. See for example, U.S. Pat. Nos. 6,007,889,and 6,280,811. Thus multiple-layer disc can be constructed andmanufactured at low cost. Combined with objective lens having anumerical aperture (NA) of 0.60, and playback lasers having a wavelengthof about 650 nm, multiple-layer optical storage devices with thecapacity to store 14 gigabytes of information (DVD-14) or 18 gigabytes(DVD-18) of information storage capacity can be made.

Various formats for the next generation optical discs have beenproposed. One of these is referred to so as a “Blu-ray” disc. TheBlu-ray disc system is characterized by a playback laser operating at awavelength of about 405 nm (blue light) and an objective lens with anumerical aperture of 0.85. The storage capacity of this device, usedwith one information layer, is estimated to be about 25 gigabytes forthe prerecorded format. Such devices have track pitch values in the 0.32μm range and channel bit length on the order of 0.05 μm.

Because the focal depth of an objective lens with a NA of 0.85 istypically less than one micron, the tolerance of the optical path lengthvariation is drastically reduced relative to currently used systems.Thus a cover layer about 100 microns thick (the distance is measuredfrom the surface of the disc to the information layer) has beenproposed. The variation of the thickness of this cover layer isextremely critical to the success of this system. For example, a 2 or 3micron thickness variation in the cover layer will introduce very highspherical aberration in the playback signal, potentially degrading thesignal to an unacceptable low level.

Another major problem with the Blu-ray format is that the currentgeneration of production equipment used for DVDs cannot be used toproduce discs with the Blu-ray format, because the proposed format istoo different from currently used DVD format. The need to invest in newequipment to manufacture Blu-ray discs substantially increases the costof making the Blu-ray disc, and presents another obstacle to adoptingthe Blu-ray disc system as the standard for the next generation of DVD.

In part, because of the aforementioned problems associated with theBlu-ray disc, another format for the next generation of DVD has beenproposed. This proposed format is sometimes referred to as the,“Advanced Optical Disc” (AOD).

The AOD format preserves some of the features of the currently used DVD,for example, an AOD comprises two 0.6 mm thick half-discs glued togetherto create a symmetrical structure. The proposed AOD system uses aplayback laser with a wavelength of 405 nm and an objective lens with aNA of about 0.65. The storage capacity of the prerecorded type of AODdisc with one information layer is about 15 gigabytes. Althoughmanufacturing an AOD disc is less complicated and less challenging thanmanufacturing a Blu-ray disc, AOD suffers one drawback. The playbacksignal quality of an AOD disc is strongly dependant upon the flatness ofthe disc. In order to deal with the variation of disc flatnessintroduced in the mass production of AOD discs, a tilt servo mechanismin the player is most likely required. The need for this mechanism willincrease the cost of players designed to read AOD discs.

Currently, there is an interest in adapting CD-RW techniques to the DVDfield to produce a rewritable DVD (DVD-RW). Some difficulties in theproduction of a DVD-RW have arisen due to the higher information densityrequirements of the DVD format. For example, the reflectivity of thereflective layer must be increased relative to that of the standard DVDreflective layer to accommodate the reading, writing, and erasingrequirements of the DVD-RW format. Also, the thermal conductivity of thereflective layer must also be increased to adequately dissipate the heatgenerated by both the higher laser power requirements to write and eraseinformation and the microstructural changes occurring during theinformation transfer process. The potential choice of the reflectivelayer is currently pure gold, pure silver and aluminum alloys. Goldseems to have sufficient reflectivity, thermal conductivity, andcorrosion resistance properties to work in a DVD-RW disk. Additionally,gold is relatively easy to sputter into a coating of uniform thickness.But once again, gold is also comparatively more expensive than othermetals, making the DVD-RW format prohibitively expensive. Pure silverhas higher reflectivity and thermal conductivity than gold, but itscorrosion resistance is relatively poor as compared to gold. Aluminumalloy's reflectivity and thermal conductivity is considerably lower thaneither gold or silver, and therefore it is not necessarily a good choicefor the reflective layer in DVD-RW or DVD+RW.

For the convenience of the reader, additional details regarding themanufacture and construction of DVD discs can be found in U.S. Pat. No.5,640,382 to Florczak et al. the disclosure of which is herebyincorporated by reference.

Therefore, what is needed are some new alloys that have the advantagesof gold when used as a reflective layer or as a semi-reflective layer inan optical storage medium, but are not as expensive as gold. These newalloys should also have better corrosion resistance than pure silver.The current invention addresses that need.

SUMMARY OF THE INVENTION

One embodiment provides metallic alloys for use in thin film reflectivelayers, these alloys have high reflectivity, sputtering characteristicssimilar to gold, are corrosion resistant, and are generally lessexpensive than gold. A number of these alloys can also be used assemi-reflective layers (coatings) in optical storage devices such asDVD-dual layer devices.

One embodiment, provides silver-based alloys with sufficient chemical,thermal and optical properties to satisfy the functional requirements ofthe reflective layer in a DVD-RW or DVD+RW disc and other current orfuture generations of optical discs in which reflectivity, corrosionresistance, and ease of application are all important requirements for alow cost and high performance product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical storage system according to one embodiment.

FIG. 2 is an optical storage system according to another embodiment,wherein an organic dye is used as a recording layer.

FIG. 3 is an optical storage system according to another embodimenthaving two layers of information pits where the playback of both layersis from one side.

FIG. 4 is an optical storage system according to another embodimenthaving three layers of information pits where the playback of all threelayers is from one side.

FIG. 5 is an optical storage system according to another embodiment,wherein the system contains a rewritable information layer.

FIG. 6 is an optical storage system according to another embodiment,wherein the system contains a rewritable information layer.

FIG. 7 is an optical storage system according to another embodiment forexample a DVD-14.

FIG. 8 is an optical storage system according to another embodiment forexample a DVD-18.

FIG. 9 is an optical storage system according to another embodiment, anoptical storage system of the Blu-ray type with layers suitable for highdensity digital information storage readable from one side.

FIG. 10 is an optical storage system according to another embodiment, anoptical storage system of the Blu-ray type including two re-writablehigh density digital information storage layers readable andre-recordable from one side.

FIG. 11 is an optical storage system according to another embodiment, anoptical storage system of the Advanced Optical Disc (AOD) type includingtwo high density digital information storage layers readable from oneside.

FIG. 12 is an optical storage system according to another embodiment, anoptical storage system of the Advanced Optical Disc (AOD) type includingtwo re-writable high density digital information storage layers readableand re-recordable from one side.

FIG. 13 is an optical storage system according to still anotherembodiment, which includes two readable and recordable layers readableand recordable from one side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Specific language is used in the following description and examples topublicly disclose the invention and to convey its principles to others.No limits on the breadth of the patent rights based simply on usingspecific language are intended. Also included are any alterations andmodifications to the descriptions that should normally occur to one ofaverage skill in this technology.

As used in this specification the term “atomic percent” or “a/o percent”refers to the ratio of atoms of a particular element or group ofelements to the total number of atoms that are identified to be presentin a particular alloy. For example, an alloy that is 15 atomic percentelement “A” and 85 atomic percent element “B” could also be referencedby a formula for that particular alloy: A_(0.15)B_(0.85).

As used herein the term “of the amount of silver present” is used todescribe the amount of a particular additive that is included in thealloy. Used in this fashion, the term means that the amount of silverpresent, without consideration of the additive, is reduced by the amountof the additive that is present to account for the presence of theadditive in a ratio. For example, if the relationship between Ag and anelement “X” is Ag_(0.85) X_(0.15) (respectively 85 a/o percent and 15a/o percent) without the considering the amount of the additive that ispresent, and if an additive “B” is present at a level 5 atomic percent“of the amount of silver present”; then the relationship between Ag, X,and B is found by subtracting 5 atomic percent from the atomic percentof silver, or the relationship between Ag, X, and B isAg_(0.80)X_(0.15)B_(0.05) (respectively 80 a/o percent silver, 15 a/opercent “X”, and 5 a/o percent “B”).

As used in this specification the term “adjacent” refers to a spatialrelationship and means “nearby” or “not distant.” Accordingly, the term“adjacent” as used in this specification does not require that items soidentified are in contact with one another and that they may beseparated by other structures. For example, referring to FIG. 5, layer424 is “adjacent” or “nearby” layer 422, just as layer 414 is “adjacent”or “nearby” layer 422.

One embodiment comprises multi-layer metal/substrate compositions thatare used as optical data storage media. One embodiment is shown in FIG.1 as optical data storage system 10. Optical storage medium 12 comprisesa transparent substrate 14, and a highly reflective thin film layer orcoating 20 on a first data pit pattern 19. An optical laser 30 emits anoptical beam toward medium 12, as shown in FIG. 1. Light from theoptical beam that is reflected by thin film layer 20 is sensed bydetector 32, which senses modulations in light intensity based on thepresence or absence of a pit or land in a particular spot on the thinfilm layer. The disc is unique in that one of the alloys presented belowis deposited upon the information pits and lands and is used as thehighly reflective thin film 20. In one alternative (not shown), the discmay be varied by attaching two optical storage media 12 back-to-back,that is, with each transparent substrate 14 facing outward.

Another embodiment is shown in FIG. 2 as optical data storage system110. Optical storage medium 112 comprises a transparent substrate 114,and a highly reflective thin film layer 120, over a layer of dye 122,placed over a first pattern 119. An optical laser 130 emits an opticalbeam toward medium 112, as shown in FIG. 2. As discussed earlier, datais placed upon the disc by deforming portions of the dye layer with alaser. Thereafter, the disc is played by light from the optical beam,which is reflected by thin film layer 120 and sensed by detector 132.Detector 132 senses modulations in light intensity based on the presenceor absence of a deformation in the dye layer. The disc is unique in thatone of the alloys presented below is deposited over the dye layer 122and is used as the highly reflective thin film or coating 120. In onealternative (not shown), the disc may be varied by attaching two opticalstorage media 112 back-to-back, that is, with each transparent substrate114 facing outward.

Another embodiment is shown in FIG. 3 as optical data storage system210. Optical storage medium 212 comprises a transparent substrate 214, apartially reflective thin film layer or coating 216 on a first data pitpattern 215, a transparent spacer layer 218, and a highly reflectivethin film layer or coating 220 on a second data pit pattern 219. Anoptical laser 230 emits an optical beam toward medium 212, as shown inFIG. 3. Light from the optical beam that is reflected by either thinfilm layer 216 or 220 is sensed by detector 232, which sensesmodulations in light intensity based on the presence or absence of a pitin a particular spot on the thin film layers. The disc is unique in thatone of the alloys presented below is deposited upon the information pitsand lands and used as the highly reflective thin film 220 orsemi-reflective layer 216. In another alternative (not shown), the discmay be varied by attaching two optical storage media 212 back-to-back,that is, with each transparent substrate 214 facing outward. Theattachment method could be by UV cured adhesive, hot melt adhesive orother type of adhesives.

Another embodiment is shown in FIG. 4 as optical data storage system310. Optical storage medium 312 comprises a transparent substrate 314, apartially reflective thin film layer or coating 316 or layer “zero” on afirst data pit pattern 315, a transparent spacer layer 318, anotherpartially reflective thin film layer or coating 320 or layer “one” on asecond data pit pattern 319, a second transparent spacer layer 322, anda highly reflective thin film layer or coating 324 or layer “two” on athird pit pattern 323. An optical laser 330 emits an optical beam towardmedium 312, as shown in FIG. 4. Light from the optical beam that isreflected by thin film layer 316, 320 or 324 is detected by detector332, which senses modulation in light intensity based on the presence orabsence of a pit in a particular spot on the thin film layers. The discis unique in that any or all of the alloys presented below can bedeposited upon the information pits and lands and used as the highlyreflective thin film or coating 324 or the semi-reflective layer orcoating 316 and 320. To playback the information on Layer 2, the lightbeam from laser diode 330 is going through the transparent polycarbonatesubstrate, passing through the first semi-reflective Layer 0, and thesecond semi-reflective Layer 1 and then reflected back from layer 2 tothe detector 332. In another alternative (not shown), the disc may bevaried by attaching two optical storage media 312 back-to-back, that is,with each transparent substrate 314 facing outward. The attachmentmethod could be by UV cured adhesive, hot melt adhesive or other type ofadhesives.

Still another embodiment is shown in FIG. 5 as optical data storagesystem 410. Optical storage medium 412 comprises a transparent substrateor a transparent layer 414, a dielectric layer 416 on a first data pitpattern 415, a recording layer 418 made of a material having amicrostructure including domains or portions capable of repeatedlyundergoing laser-induced transitions from a first state to a secondstate and back again (i.e., an optically re-recordable or rewritablelayer), such as a phase change material or a magneto-optic material,another dielectric material 420, a highly reflective thin film layer422, and a transparent substrate or layer 424. As used in thisspecification, a dielectric material is a material that is an electricalinsulator or in which an electric field can be sustained with a minimumdissipation of power. The different layers 414, 416, 418, 420 and 422 ofthe optical storage medium 410 are preferably oriented so as to beadjacent with one another.

Commonly used phase change materials for the recording layer 418 includegermanium-antimony-tellurium (Ge—Sb—Te),silver-indium-antimony-tellurium (Ag—In—Sb—Te),chromium-germanium-antimony-tellurium (Cr—Ge—Sb—Te) and the like.Commonly used materials for the dielectric Layer 416 or 420 include zincsulfide-silica compound (ZnS.SiO₂), silicon nitride (SiN), aluminumnitride (AlN) and the like. Commonly used magneto-optic materials forthe recording layer 418 include terbium-iron-cobalt (Tb—Fe—Co) orgadolinium-terbium-iron (Gd—Tb—Fe). An optical laser 430 emits anoptical beam toward medium 412, as shown in FIG. 5. In the recordingmode for the phase change recordable optical medium, light from theoptical beam is modulated or turned on and off according to the inputdigital data and focused on the recording layer 418 with suitableobjective while the medium is rotated in a suitable speed to effectmicro-structural or phase change in the recording layer. In the playbackmode, the light from the optical beam that is reflected by the thin filmlayer 422 through the medium 412 is sensed by the detector 432, whichsenses modulations in light intensity based on the crystalline oramorphous state of a particular spot in the recording layers. The discis unique in that one of the alloys presented below is deposited uponthe medium and used as the highly reflective thin film 422. In anotheralternative (not shown), the disc may be varied by attaching two opticalstorage media 412 back-to-back, that is, with each transparent substrateor coating 414 facing outward. The attachment method could be by UVcured adhesive, hot melt adhesive or other type of adhesives.

As shown in FIG. 5, if the thickness of the transparent substrate 414 isabout 1.2 mm thick made of injection molded polycarbonate withcontinuous spirals of grooves and lands, 424 is a UV cured acrylic resin3 to 15 micron in thickness acting as a protective layer with theplayback laser 430 at 780 to 820 nanometer, and the rewritable layer 418is a phase change material of a typical composition such as Ag—In—Sb—Te,it is a structure of a compact disc-rewritable disc, or commonly knownas CD-RW. To record and read information, phase change discs utilize therecording layer's ability to change from an amorphous phase with lowreflectivity (dark) to a crystalline phase with high reflectivity(bright). Before recording, the phase change layer is in a crystallinestate. During recording, a laser beam with high power focused on therecording layer will heat the phase change material to high temperatureand when the laser is turned off, the heated spot cools off very fast tocreate an amorphous state. Thus a series of dark spots of amorphousstates are created according to the input data of turning the focusedlaser beam on and off. These on and off correspond to “0” and “1” of adigital data stream.

In reading, a low laser power is used to focus on and read the dark orbright spots along the track of the disc to play back the recordedinformation. To erase, an intermediate laser power is used to focus onthe grooves or tracks with the disc spinning so that an intermediatetemperature of the focused spots is reached. After the laser spots aremoved to another location, the spots cool to room temperature with acrystalline structure of high reflectivity. This returns the recordinglayer to its original or erased state. The change of the spots fromamorphous to crystalline state is very reversible, thus many record anderase cycles can be accomplished and different data can be repeatedlyrecorded and read back with no difficulty.

If the thickness of the transparent substrate 414 is about 0.5 to 0.6 mmthick made of injection molded polycarbonate with continuous spirals ofgrooves and lands, with 416 and 420 being the dielectric layers made oftypically ZnS.SiO₂, and 418 is made of a phase change material such asAg—In—Sb—Te or Ge—Sb—Te, with 422 made of a silver alloy disclosedherein, and 424 is a UV cured resin bonding another half of the samestructure as depicted in FIG. 5, with the read and write laser 430 at630 to 650 nanometer wavelength, then it is a digital versatile discwith rewritable capability or commonly referred to as DVD+RW. Somepreferred phase-changeable materials include materials from thefollowing series: As—Te—Ge, As—In—Sb—Te, Te—Ge—Sn, Te—Ge—Sn-0, Te—Se,Sn—Te—Se, Te—Ge—Sn—Au, Ge—Sb—Te, Sb—Te—Se, In—Se—Tl, In—Sb, In—Sb—Se,In—Se—Tl—Co, Cr—Ge—Sb—Te and Si—Te—Sn, where As is arsenic, Te istellurium, Ge is germanium, Sn is tin, O is oxygen, Se is selenium, Auis gold, Sb is antimony, In is indium, Ti is thallium, Co is cobalt, andCr is chromium. In this disc configuration, the highly reflective layer422 needs not only high reflectivity at 650 nanometer wavelength andhigh thermal conductivity, but also high corrosion resistance againstZnS.SiO₂. Conventional aluminum alloy do not have high enoughreflectivity nor high enough thermal conductivity. Pure silver or otherconventional silver alloys do not have either high corrosion resistanceor high reflectivity and high thermal conductivity. Thus it is anotherembodiment to provide a series of silver alloys that can meet therequirements for this application.

Another embodiment is shown in FIG. 6 as an optical information storagesystem 510 of the rewritable type. Transparent cover layer 514 isapproximately 0.1 mm in thickness. Dielectric layers 516 and 520 arepreferably made of ZnS.SiO₂ and serve as a protective layer for therewritable layer or phase change layer 518. Rewritable layer 518 ispreferably formed from Ag—In—Sb—Te or the like. Highly reflective layer522 is preferably formed from a silver alloy, such as disclosed herein.Transparent substrate 524 is preferably approximately 1.1 mm inthickness with continuous spiral tracks of grooves and land usually madewith polycarbonate resin. Laser 530 preferably has a wavelength of about400 nm with associated optics to focus the laser beam on to therecording layer 518. The reflected laser beam is received by thedetector 532, which preferably includes associated data processingcapability to read back the recorded information. This system 510 issometimes called a “Digital Video Recording System” or DVR designed torecord high definition TV signal. The principle of operation of thisoptical information storage system 510 is about the same as a CD-RW discexcept the recording density is considerably higher and the storagecapacity of a 5-inch diameter disc is approximately 20 gigabytes. Againthe performance of the disc stack depends on a highly reflective, layer522 at 400 nm wavelength with high corrosion resistance and very highthermal conductivity. Conventional reflective layer such as aluminum,gold or copper all have difficulty meeting this requirement. Thus it isanother embodiment to provide a silver alloy reflective layer that iscapable of meeting these demanding requirements.

Other optical recording media which can be used to practice thisinvention include for example optical storage devices readable and insome embodiments also rewritable from both sides of the device.

One embodiment is illustrated in FIG. 7 optical data storage system 610.Optical storage system 610 is sometimes referred to as DVD-14 and isillustrative of devices that have the capacity to store accessible dataon both sides of the structure.

Optical storage system 610 comprises a 0.6 mm thick transparentpolycarbonate substrate (PC), adjacent to the PC layer or a part of thePC layer is a first data pit pattern 614 comprising a series of pits andlands. Adjacent to layer 614 and conforming to the contour of layer 614is a semi-reflective layer or coating 618. Adjacent to the layer orcoating 618 is a spacer 622 comprised of a transparent material adjacentto or a part of spacer layer 622 is a second data pit pattern 626comprising a series of pits and lands. Adjacent to and conforming to thecontour of second data pit pattern 626 is a reflective layer or coating630. Both semi-reflective layer or coating 618 and highly reflectivelayers 630 can be read from the same side of structure 610.

Adjacent to layer or coating 634 is a second reflective layer or coating638. Layer or coating 638 is adjacent to and conforms to the contours ofa third data pit pattern 642 comprising a series of pits and lands.Third data pit pattern 642 and highly reflective layer or coating 638are readable from the side of the device opposite to the side of thedevice from which data pit patterns 618, 626 are read. Adjacent to orcomprising data pit pattern 642 is a second 0.6 mm thick polycarbonatelayer.

An optical laser 660 emits an optical beam towards second polycarbonatelayer PC, the beam is reflected by highly, reflective layer or coating638 and sensed by detector 662 modulations in light intensity based onthe presence or absence of a pit in a particular spot on the highlyreflective coating or layer.

As illustrated in FIG. 7, from the side of device 610 opposite of laser660, a second optical beam from laser 650 is directed towards firstpolycarbonate substrate layer PC towards data pit pattern 614. Asillustrated in FIG. 7, the second laser 650 emits an optical beamtowards semi-reflective layer or coating 618 and highly reflective layer630. At least a portion of the optical beam emitted by laser 650 passesthrough semi-reflective layer 618 to reach reflective layer 626. Lightfrom the optical beam that is reflected by layer or coating 626 issensed by detector 652, which senses modulations in light intensitybased on the presence or absence of a pit or land in a particular spoton the highly reflective layer.

While the optical storage device illustrated in FIG. 7 comprisesmultiple laser sources 650, 660 and multiple detectors 652, 662, thesame could be accomplished using a single laser source and detectorconfigured such that the same optical beam source and detector can beused to collect signals from all sets of information pits and landscomprising the device, for example set 618, 626, 642.

Still another embodiment is the optical storage system 710 asillustrated in FIG. 8. Optical storage medium 710 is illustrative of aDVD-18 and is representative of optical storage systems that havemultiple information layers readable from both sides of the opticalstorage medium.

Optical storage system 710 comprises a 0.6 mm thick transparentsubstrate 712 adjacent to, or comprising a first data pit pattern 714.Data pit pattern 714 comprises a series of pits and lands and isadjacent to a semi-reflective layer or coating 716. The device furtherincludes a transparent spacer layer 718 about 50 microns thick, and asecond data pit pattern 720 adjacent to a highly reflective film orcoating 722. Both semi-reflective layer or coating 716 and highlyreflective layer or coating 722 can be read from the same side of 710.

An optical laser 770 emits an optical beam towards transparent layer712. As illustrated in FIG. 7 at least a portion of the optical beamemitted by laser source 770 passes through semi-reflective layer 716 toreach highly reflective layer 722. Light from the optical beam that isreflected by semi-reflective layer or coating 716 and highly reflectivelayer 722 is sensed by detector 772, which senses modulations in lightintensity based on the presence or absence of a pit or land in aparticular spot on the highly reflective layer or the semi-reflectivelayer.

The optical storage device illustrated in FIG. 8 further includes thespacer layer 724, which connects the portion of the device comprisingthe first two information layers 714, 720 with the portion of the devicecomprising the third and fourth information layers 728, 734. Substratelayer 724 is adjacent to and separates highly reflective layer orcoating 728 and highly reflective layer or coating 722.

Highly reflective layer or coating 724 is adjacent to, and conforms tothe contours of the pit and lands or data pit pattern layer 728. Layer728 is adjacent to spacer layer 726, spacer layer 726 is adjacent tosemi-reflective layer 732, which is adjacent to, and conforms to thecontours of data pit pattern layer 734. Data pit pattern layer 734 iscontiguous with, or adjacent to, 0.6 mm thick substrate layer 736.

In the embodiment illustrated in FIG. 8 an optional second optical laser780 is provided which emits an optical beam towards layer 736. A portionof the light emitted by laser 780 passes through semi-reflective layeror coating 732 and is reflected by highly reflective layer or coating724 light reflected by semi-reflective layer or coating 732 and highlyreflective layer 724 is sensed by detector 782, which senses modulationsin light intensity based on the presence or absence of a pit or land ina particular spot on the highly reflective layer.

While the optical storage device illustrated in FIG. 8 includes multiplelaser sources 770, 780 and multiple detectors 752, 772, the same couldbe accomplished using a single laser source and detector configured suchthat the same optical beam source and detector can be used to collectsignals from all sets of information pits and lands comprising thedevice.

Yet another embodiment includes the proposed next generation opticalstorage device sometimes referred to as “Blu-ray.” Blu-ray devicesincorporate lasers, which operate at a wavelength of 405 nm and lenses,with a numerical aperture of 0.85.

As illustrated in FIG. 9 optical storage system 810 of the prerecordedtype of “Blu-Ray” disc comprises two sets of information pits and lands818 and 830 readable from the same side of the device. Device 810comprises transparent cover layer 814 about 0.1 mm in thickness, and asubstrate layer 838 about 1.1 mm thickness with an adjacent highlyreflective layer or coating 834. Highly reflective layer or coating 834is adjacent to, and conforms to the second data pit pattern 830injection molded onto the substrate 838. Data pit pattern 830 comprisinga set of pits and lands is adjacent to, or a part of, substrate 838.Layer 826 is adjacent to the semi-reflective layer 822. Semi-reflectivelayer or coating 822 is adjacent and conforms to first data pit pattern818 comprising a set of pits and lands. Data pit 818 is adjacent to or apart of the transparent cover layer 814.

As illustrated in FIG. 9, an optical beam source laser 850 is provided,as is detector 852. Optical laser 850 emits an optical beam towardslayer 814 through an objective lens (not shown in FIG. 9). A portion ofthe light emitted by laser 850 passes through a lens (not shown), thesemi-reflective layer, or coating, 822 and is reflected by highlyreflective layer, or coating, 834 and sensed by detector 852, whichsenses modulations in light intensity based on the presence or absenceof a pit or land in a particular spot on the highly reflective layer orcoating 822.

A portion of the optical beam emitted by optical laser 850 is partiallyreflected by semi-reflective layer or coating 822 is sensed by detector852, which senses modulations in light intensity based on the presenceor absence of a pit or land in a particular spot on semi-reflectivelayer or coating 822.

In one embodiment, as illustrated in FIG. 10, an optical storage device910 of the Blu-ray rewritable type further comprises two read andrewritable layers 926, 954. Optical storage device 910 comprises asubstrate layer 972 about 1.1 mm thick, adjacent to highly reflectivelayer or coating 968. Adjacent to layer or coating 968 is a firstdielectric layer 964 comprising ZnS—SiO₂, adjacent to layer 964 is afirst interface layer 960 such as Ge—N or others. Adjacent to layer 960is a phase-change type recording layer such as Ge—Sb—Te 954 and the likewith thickness about 10 to 15 nm, adjacent to layer 954 is layer 950 asecond layer such as Ge—N and the like. Adjacent to layer 950 is layer946 a second dielectric layer of ZnS—SiO₂.

Optical storage device 910 further includes an intermediate layer 942sandwiched between the dielectric layer 946 approximately 20 to 40microns thick and a semi-reflective layer or coating 938 about 10 nmthick. A third dielectric layer 934 comprised of ZnS—SiO₂ is adjacent tolayer or coating 938. Adjacent to layer 934 is a third interface layer930 made with Ge—N or others, a recording layer 926 6-10 nm thickcomprised of Ge—Sn—Sb—Te or other phase-change material is sandwichedbetween layers 930 and a fourth interface layer 922 made of Ge—N and thelike. Adjacent to layer 922 is a fourth layer of dielectric materiallayer 918 comprised of ZnS—SiO₂. Adjacent to layer 918 is a transparentcover layer 914 about 80 to 100 microns thick.

As illustrated in FIG. 10 an optical beam emitted by laser 970 passesthrough layers 914, 918, 922, 926, 930, 934 and is reflected by layer938 and sensed by detector 972. A portion of an optical beam emitted bylaser 970 passes through layers 914, 918, 922, 926, 930, 934, 938, 942,946. 950, 954, 960, 964, and is reflected by layer 968 to and sensed bydetector 972. All the silver alloy compositions disclosed can be usedfor the semi-reflective layer 938 or the highly reflective layer 968. Inthe recording mode, the laser beam from laser 970 will be focused on thephase-change layer 926 or 954 to change its reflectivity propertiessimilar to a conventional CD-RW, DVD-RW, DVD+RW or next generation ofoptical discs with playback laser wavelength at around 400 nm asdisclosed in prior art such as U.S. Pat. Nos. 6,544,616, 6,652,948,6,649,241 and others.

It is understood that the disc structure as described in FIG. 11 can bemodified that both 1014 and 1060 can be of approximately of the samethickness or around 0.6 mm and with similar phase-change materialrecording stack, the disc structure could be a rewritable optical discof the “Advanced Optical Disc” or AOD type wherein the recording andplayback laser wavelength is around 400 nm.

It is further understood that all the optical disc structures asdescribed in FIGS. 7, 8, 9, 12 contain a dual layer disc structure ofthe prerecorded type wherein the playback laser beam has a wavelength ofaround 635 to 650 nm as in FIGS. 7 and 8, or contain a dual layer HD-DVDdisc structure wherein the playback laser has a wavelength around 400 nmor any other optical disc structure with two or more layers ofinformation all recorded or played back from one side of the disc inwhich a semi-reflective layer or layers of silver alloy as disclosed inthis invention is made useful.

One embodiment, as illustrated in FIG. 11 is an optical storage device1010 of the ‘Blu-ray’ configuration further comprising two write oncelayers 1048 and 1024. Optical storage device 1010 is a dual-layer writeonce recording medium comprised of 1.1 mm thick substrate layer 1060,adjacent to a highly reflective layer 1056 about 30 to 60 nm thickusually made with silver alloy of the current invention or an aluminumalloy. Layer 1056 is adjacent to protective layer 1052, layer 1052 isadjacent to a recordable layer 1048, 15 to 25 nm thick comprised ofTe—O-Pd based material or others. Layer 1048 is adjacent to protectivefilm layer 1044.

Layer 1044 is adjacent to a separation layer or spacer layer 1040 whichis adjacent to a 10 nm thick semi-reflective layer or coating 1034 madewith silver alloy of the current invention. Layer or coating 1034 isadjacent to protective film layer 1030 which is adjacent to a second 10nm thick recording layer 1024 comprising Te—O—Pd based material orothers. Layer 1024 is adjacent to protective film 1020 which is adjacentto a 0.075 mm thick cover layer 1014.

As illustrated in FIG. 11, an optical beam emitted by laser 1070 passesa lens system with NA 0.85 (not shown) in FIG. 11 through layers 1014,1020, 1024, 1030 and is reflected by the semi-reflective layer 1034 andsensed by detector 1072. A portion of an optical beam emitted by laser1070 passes through layers 1014, 1020, 1024, 1030, 1034, 1040, 1044,1048, 1052, and is reflected by highly reflective layer 1056 and sensedby detector 1072. Detector 1072 senses modulations in light intensitybased on the amorphous or the crystalline state of the layer 1024 or1048 in a particular spot on semi-reflective layer or coating 1034 andon the highly reflective layer 1056 and reads the stored informationback by focusing laser light from 1070 laser on the write-once layer1024 or 1048. The spacer layer 1040 should be thick enough so that whenthe read beam is focused on the recordable layer 1024, the read beam issufficiently defocused on the next recordable layer 1048 and only themodulation of light information from 1024 is reflected back to thedetector 1072. Conversely, when the read beam is focused on therecordable layer 1048, the read beam is sufficiently defocused on theother recording layer 1024 and only the modulation from 1048 isreflected to the detector 1072 and read.

It is also understood that as described in FIGS. 10 and 11, a dual layerdisc of the write-once or a rewritable type with a phase changerecording layer or other types of recording layers can be constructedsuch that at least two recording layers can be recorded and read fromone side or the same side of the disc wherein a semi-reflective layermade with silver alloy of the current invention can be utilized and madeuseful.

Another embodiment, as illustrated in FIG. 12, is optical storage device1110 of a prerecorded type, which is the proposed next generationoptical storage device sometimes referred to as an Advanced OpticalDevice (AOD). AOD is a system that uses a 405 nm wavelength laser beamand a lens system with a NA of 0.65 to record and retrieve informationfor both faces of an optical storage device wherein the transparentsubstrates 1120 and 1140 made typically with injection moldedpolycarbonate are approximately 0.6 mm thick.

Device 1110 comprises a transparent substrate layer 1140 adjacent to ahighly-reflective layer or coating 1136 which is adjacent to andconforms to the contours of a first data pit pattern 1138 comprising aset of pits and lands. High reflectivity layer 1136 is adjacent tospacer layer 1132 which is adjacent to a semi-reflective layer orcoating 1124 of the current invention which is adjacent to and conformsto the contours of a second data pit pattern 1128 comprising a series ofpits and lands. Layer 1124 is adjacent to a second substrate or layer1120.

As illustrated in FIG. 12, a portion of an optical beam emitted by laser1150 passes through layers 1120, 1124, 1128, 1132, and is reflected bythe highly reflective layer 1136 and sensed by detector 1152. A portionof an optical beam emitted by laser 1150 passes through layers 1120, andis reflected by semi-reflective layer or coating 1124 and sensed bydetector 1152. Detector 1152 senses modulations in light intensity basedon the presence or absence of a pit or land in a particular spot onsemi-reflective layer or coating 1124 and the highly reflective layer orcoating 1136 by focusing on layer 1124 or 1136.

In another embodiment, illustrated in FIG. 13 an optical storage device1210 of the organic dye recordable-dual-layer type comprises two layerswhich are both readable and recordable from the same side of the device.Device 1210 comprises a transparent substrate layer 1214 adjacent tofirst recordable dye layer 1218. Dye layer 1218 is adjacent tosemi-reflective layer or coating 1222 of the current invention. Layer orcoating 1222, sometimes called “Layer zero” or L0, is adjacent to spacerlayer 1226. Spacer layer 1226 is adjacent to a second dye recordinglayer 1230. Layer 1230 is adjacent to highly reflective layer or coating1234. Reflective layer or coating 1234, sometimes called “layer one” orL1 is adjacent to polycarbonate substrate or layer 1238.

In write mode, as illustrated in FIG. 13, optical beam source 1250 emitsa laser beam which passes through layers 1214, and is focused on dyelayer 1218. When laser 1250 is operating at high intensity the opticalbeam focused on layer 1218 decomposes the dye in layer 1218 creating adata pit pattern comprising the equivalent of a series of pits andlands. A portion of an optical beam emitted by laser 1250 passes throughlayers 1214, 1218, 1222, 1226 and is focused on dye layer 1230. Whenlaser 1250 is operating at high intensity, the optical beam focused onlayer 1230 decomposes the dye in layer 1230 to create a data pit patterncomprising a series of pits and lands.

In read mode a portion of an optical beam emitted by laser 1250 passesthrough transparent polycarbonate layer 1214 and dye layer 1218, isreflected by the semi-reflective layer or coating 1222 and sensed bydetector 1252. A portion of the optical beam also passes through layers1214, 1218, 1222, 1226, 1230 and is reflected by highly reflective layer1234 and sensed by detector 1252. Detector 1252 senses modulations inlight intensity based on the presence or absence of a pit or land in aparticular spot on the reflective layer or coating 1234 or by thesemi-reflective layer or coating 1222 depending on whether the laserlight 1250 is focused on the semi-reflective layer 1222 or the highlyreflective layer 1234. For the general operation of an organic dye-basedoptical recording medium, the reader can refer to U.S. Pat. Nos.6,641,889, 6,551,682, etc.

It is further understood that the optical disc structure as described inFIG. 13 can be a dual layer DVD-R or DVD+R disc wherein the playbacklaser beam has a wavelength of around 635 to 650 nm, or the structurecan be a dual layer HD-DVD-R disc wherein the playback laser has awavelength around 400 nm or any other optical disc structure wherein twoor more layers of information can all be recorded or played back fromone side of the disc in which a semi-reflective layer or layers ofsilver alloy as disclosed in this invention is made useful.

As used herein, the term “reflectivity” refers to the fraction ofoptical power incident upon transparent substrate 14, 114, 214, 314, 414or 514 which, when focused to a spot on a region of layer 20, 120, 216,220, 316, 320, 324, 422 or 522 could in principle, be sensed by aphotodetector in an optical readout device. It is assumed that thereadout device includes a laser, an appropriately designed optical path,and a photodetector, or the functional equivalents thereof.

This invention is based on the observation that particular silver-basedalloys provide sufficient reflectivity and corrosion resistance to beused as the highly reflective or the semi-reflective layer in an opticalstorage medium, without the inherent cost of a gold-based alloy or theprocess complication of a silicon-based material. In one embodiment, thesilver is alloyed with a comparatively small amount of zinc. In thisembodiment, the relationship between the amounts of zinc and silverranges from about 0.01 a/o percent (atomic percent) to about 15 a/opercent zinc and from about 85 a/o percent to about 99.99 a/o percentsilver. But preferably in respect to each metal, the alloy has fromabout 0.1 a/o percent to about 10.0 a/o percent zinc and from about 90.0a/o percent to about 99.9 a/o percent silver.

In another embodiment, the silver is alloyed with a comparatively smallamount of aluminum. In this embodiment, the relationship between theamounts of aluminum and silver ranges from about 0.01 a/o percent(atomic percent) to about 5 a/o percent aluminum and from about 95 a/opercent to about 99.99 a/o percent silver. But preferably in respect toeach metal, the alloy has from about 0.1 a/o percent to about 3.0 a/opercent aluminum and from about 97 a/o percent to about 99.9 a/o percentsilver.

In another embodiment, the silver-based, binary alloy systems asmentioned above are further alloyed with cadmium (Cd), lithium (Li), ormanganese (Mn). If one or more of these metals replaces a portion of thesilver in the alloy, the corrosion resistance of the resultant thin filmwill likely increase; however, the reflectivity will also likely drop.The amount of cadmium, lithium, or manganese that may favorably replacesome of the silver in the binary alloy ranges from about 0.01 a/opercent to about 20 a/o percent of the amount of silver present forcadmium, from about 0.01 a/o percent to about 10 a/o percent or even toabout 15 a/o percent of the amount of silver present for lithium, andfrom about 0.01 a/o percent to about 7.5 a/o percent of the amount ofsilver present for manganese.

In still another embodiment, the silver-based, zinc and aluminum binaryalloy systems as mentioned above are further alloyed with a preciousmetal such as gold (Au), rhodium (Rh), copper (Cu), ruthenium (Ru),osmium (Os), iridium (Ir), platinum (Pt), palladium (Pd), and mixturesthereof, which may be added to the above binary alloys with thepreferable range of precious metal to be about 0.01 a/o to 5.0 a/opercent of the amount of silver present. In addition to the preciousmetals, the above alloys may be still further alloyed with a metal suchas titanium (Ti), nickel (Ni), indium (In), chromium (Cr), germanium(Ge), tin (Sn), antimony (Sb), gallium (Ga), silicon (Si), boron (B),zirconium (Zr), molybdenum (Mo), and mixtures thereof. In relation tothe amount of silver that is present in the above silver alloy system,the amount of these metals that may be preferably added ranges fromabout 0.01 a/o percent to about 5.0 a/o of the amount of silver present.

In still another embodiment, the silver is alloyed with a comparativelysmall amount of both zinc and aluminum. In this embodiment, therelationship between the amounts of zinc, aluminum and silver rangesfrom about 0.1 a/o percent to about 15 a/o percent zinc, from about 0.1a/o percent to about 5 a/o percent aluminum, and from about 80 a/opercent to about 99.8 a/o percent silver. But preferably in respect toeach metal, the alloy has from about 0.1 a/o percent to about 5.0 a/opercent zinc, from about 0.1 a/o percent to about 3.0 a/o percentaluminum, and from about 92.0 a/o percent to about 99.8 a/o percentsilver.

In yet another embodiment, the silver-based zinc-aluminum ternary alloysystem as mentioned above is further alloyed with a fourth metal. Thefourth metal may include manganese or nickel. If one or a mixture ofthese metals replaces a portion of the silver in the alloy, thecorrosion resistance of the resultant thin film will likely increase;however, the reflectivity will also likely drop. The amount of manganeseor nickel that may favorably replace some of the silver in the aboveternary alloy ranges from about 0.01 a/o percent to about 7.5 a/opercent of the amount of silver present for manganese, with a preferablerange being between about 0.01 a/o percent and about 5.0 a/o percent ofthe amount of silver present. The amount of nickel may range frombetween about 0.01 a/o percent to about 5.0 a/o percent of the amount ofsilver present with a preferable range being between from about 0.01 a/opercent and about 3.0 a/o percent of the amount of silver present.

In still another embodiment, the silver-based zinc-aluminum ternaryalloy system as mentioned above is further alloyed with a precious metalsuch as gold, rhodium, copper, ruthenium, osmium, iridium, platinum,palladium, and mixtures thereof, which may be added to the above ternaryalloys with the preferable range of precious metal to be about 0.01 a/oto 5.0 a/o percent of the amount of silver present. In addition to theprecious metals, the above alloys may also be alloyed with a metal suchas titanium, nickel, indium, chromium, germanium, tin, antimony,gallium, silicon, boron, zirconium, molybdenum, and mixtures thereof. Inrelation to the amount of silver that is present in the above silveralloy system, the amount of such metals that may be preferably addedranges from about 0.01 a/o percent to about 5.0 a/o percent of theamount of silver present.

In another embodiment an optical storage medium comprises a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer is made of a silver and zinc alloy where the relationship betweenthe amount of silver and the amount of zinc is defined by Ag_(x)Zn_(y)where 0.85<x<0.9999 and 0.0001<y<0.15.

In another embodiment an optical storage medium comprises a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer is made of a silver and aluminum alloy where the relationshipbetween the amount of silver and the amount of aluminum is defined byAg_(x)Al_(z) where 0.95<x<0.9999 and 0.0001<x<0.05.

In another embodiment an optical storage medium comprises a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer is made of a silver and zinc and aluminum alloy where therelationship between the amount of silver and the amount of zinc and theamount of aluminum is defined by Ag_(x)Zn_(y)Al_(z) where 0.80<x<0.998and 0.001<y<0.15, and 0.001<z<0.05.

In another embodiment an optical storage medium comprises a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer is made of a silver and manganese alloy where the relationshipbetween the amount of silver and manganese is defined by Ag_(x)Mn_(t)where 0.925<x<0.9999 and 0.0001<t<0.075.

In another embodiment an optical storage medium comprises a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer is made of a silver and germanium alloy where the relationshipbetween the amount of silver and the amount of germanium is defined byAg_(x)Ge_(q) where 0.97<x<0.9999 and 0.0001<q<0.03.

In another embodiment an optical storage medium comprises a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer is made of a silver and copper and manganese alloy where therelationship between the amount of silver and the amount of copper andthe amount of manganese is defined by Ag_(x)Cu_(p)Mn_(t) where0.825<x<0.9998 and 0.0001<p<0.10, and 0.0001<t<0.075.

In another embodiment, the silver is alloyed with a comparatively smallamount of manganese. In this embodiment, the relationship between theamounts of manganese and silver ranges from about 0.01 a/o percent toabout 7.5 a/o percent manganese and from about 92.5 a/o percent to about99.99 a/o percent silver. But preferably in respect to each metal, thealloy has from about 0.1 a/o percent to about 5 a/o percent manganeseand from about 95 a/o percent to about 99.9 a/o percent silver.

In yet another embodiment, the silver-based binary manganese alloysystem as mentioned above is further alloyed with a third metal. Thethird metal may include cadmium, nickel, lithium and mixtures thereof.If one or a mixture of these metals replaces a portion of the silver inthe alloy, the corrosion resistance of the resultant thin film willlikely increase; however, the reflectivity will also likely drop. Inrelation to the amount of silver that is present in the above binaryalloy systems, the amount of cadmium may be range from about 0.01 a/opercent to about 20 a/o percent of the alloy of the amount of silverpresent, the amount of nickel may range from between about 0.01 a/opercent to about 5.0 a/o percent of the amount of silver present, andthe amount of lithium may range from about 0.01 a/o percent to about10.0 a/o percent of the amount of silver present.

In still another embodiment, the silver-based manganese alloy system asmentioned above is further alloyed with a precious metal such as gold,rhodium, copper, ruthenium, osmium, iridium, platinum, palladium, andmixtures thereof, which may be added to the above binary alloys with thepreferable range of precious metal to be about 0.01 a/o to 5.0 a/opercent of the amount of silver present. In addition to the preciousmetals, the above alloys may also be alloyed with a metal such astitanium, indium, chromium, germanium, tin, antimony, gallium, silicon,boron, zirconium, molybdenum, and mixtures thereof. In relation to theamount of silver that is present in the above silver alloy system, theamount of the latter metal(s) that may be preferably added ranges fromabout 0.01 a/o percent to about 5.0 a/o percent of the amount of silverpresent.

In still another embodiment, the silver is alloyed with a comparativelysmall amount of germanium. In this embodiment, the relationship betweenthe amounts of germanium and silver ranges from about 0.01 a/o percentto about 3.0 a/o percent germanium and from about 97.0 a/o percent toabout 99.99 a/o percent silver. But preferably in respect to each metal,the alloy has from about 0.1 a/o percent to about 1.5 a/o percentgermanium and from about 98.5 a/o percent to about 99.9 a/o percentsilver.

In yet another embodiment, the silver-based germanium alloy system asmentioned above is further alloyed with a third metal. The third metalmay include manganese or aluminum. If one or a mixture of these metalsreplaces a portion of the silver in the alloy, the corrosion resistanceof the resultant thin film will likely increase; however, thereflectivity will also likely drop. In relation to the amount of silverthat is present in the above binary alloy system, the amount ofmanganese may be range from about 0.01 a/o percent to about 7.5 a/opercent of the amount of silver present and the amount of aluminum mayrange from between about 0.01 a/o percent to about 5.0 a/o percent ofthe amount of silver present.

In still another, the silver-based germanium alloy system as mentionedabove is further alloyed with a precious metal such as gold, rhodium,copper, ruthenium, osmium, iridium, platinum, palladium, and mixturesthereof, which may be added to the above binary alloys with thepreferable range of precious metal to be about 0.01 a/o to 5.0 a/opercent of the amount of silver present. In addition to the preciousmetals, the above alloys may also be alloyed with a metal such as zinc,cadmium, lithium, nickel, titanium, zirconium, indium, chromium, tin,antimony, gallium, silicon, boron, molybdenum, and mixtures thereof. Inrelation to the amount of silver that is present in the above silveralloy system, the amount of these metals that may be preferably addedranges from about 0.01 a/o percent to about 5.0 a/o percent of theamount of silver present.

In still another embodiment, the silver is alloyed with a comparativelysmall amount of both copper and manganese. In this embodiment, therelationship between the amounts of copper, manganese and silver rangesfrom about 0.01 a/o percent to about 10 a/o percent copper, from about0.01 a/o percent to about 7.5 a/o percent manganese, and from about 82.5a/o percent to about 99.98 a/o percent silver. But preferably in respectto each metal, the alloy comprises about 0.1 a/o percent to about 5.0a/o percent copper, from about 0.1 a/o percent to about 3.0 a/o percentmanganese, and from about 92.0 a/o percent to about 99.8 a/o percentsilver.

In yet another embodiment, the silver-based copper-manganese alloysystem as mentioned above is further alloyed a fourth metal. The fourthmetal such as aluminum, titanium, zirconium, nickel, indium, chromium,germanium, tin, antimony, gallium, silicon, boron, molybdenum, andmixtures thereof. In relation to the amount of silver that is present inthe above silver alloy system, the amount of the fourth metal that maybe preferably added ranges from about 0.01 a/o percent to about 5.0 a/opercent of the amount of silver present.

The optical properties of these silver alloys as thin film in thethickness of 8 to 12 nanometers for the semi reflective layer of DVD-9dual layer discs are illustrated in Table I in the following. Asmentioned in U.S. Pat. No. 5,464,619 assigned to Matsushita Electric andU.S. Pat. No. 5,726,970 assigned to Sony that in a dual layer opticaldisc structure as indicated in FIG. 3 and in Table I, the relationshipbetween the reflectivity of Layer “0” or 216 in FIG. 3 as R₀, thereflectivity of Layer “1” or 220 measured from outside the disc in FIG.3 as R₁′, and the transmission of Layer “0” as T_(o) is R₀═R₁T₀ ² whereR₁ is the reflectivity of Layer “1” itself. When the layer “0” thicknessis optimized for balanced signal and reflectivity, and Layer “1” is anconventional aluminum alloy at 50 to 60 nanometers, the balancedreflectivity of various silver alloys is shown in Table I where R is thereflectivity of the thin film achievable at 60 nanometer or higher inthickness at 650 nanometer wavelength if used as the Layer “1” or thehigh reflectivity layer of DVD-9 or any other high reflectivityapplication of optical information storage medium. All compositions inthe table are in atomic percent.

TABLE I Balance of reflectivity of Layer 0 and Layer 1 of DVD-9 duallayer disc for various silver alloy Layer 0 and typical aluminum alloyLayer 1. Composition T₀ R₀ R₁ ^(′) R Ag—13.0% Zn 0.47 0.185 0.183 0.80Ag—6.0% Zn 0.52 0.22 0.224 0.92 Ag—4.0% Zn 0.53 0.23 0.233 0.93 Ag—10.3%Cd 0.51 0.22 0.216 0.91 Ag—14.5% Li 0.53 0.23 0.232 0.93 Ag—4.3% Al 0.470.18 0.183 0.80 Ag—1.5% Al 0.53 0.23 0.234 0.93 Ag—2.0% Ni 0.54 0.2410.241 0.94 Ag—1.0% Ni 0.545 0.247 0.246 0.95 Ag—3.1% Mn 0.51 0.216 0.2140.91 Ag—1.5% Mn 0.54 0.243 0.242 0.94 Ag—0.4% Ti 0.49 0.198 0.197 0.88Ag—1.0% Zr 0.52 0.229 0.224 0.93

In still another embodiment, the sputtering target and the thin film onthe optical information storage medium is a silver alloy with acomparatively small addition of aluminum as alloying elements. In thisembodiment, the relationship between the amounts of silver and aluminumranges from about 0.01 a/o percent to about 5.0 a/o percent aluminum andfrom about 95.0 a/o percent to about 99.99 a/o percent silver. Butpreferably from about 0.1 a/o percent to about 3.0 a/o percent aluminum,and from about 97.0 a/o percent to about 99.9 a/o percent silver. Thissilver and aluminum binary alloy can be further alloyed with zinc,cadmium, lithium, manganese, nickel, titanium and zirconium or mixturesof these metals. In relation to the amount of silver that is present inthe above silver and aluminum binary alloy, the amount of theabove-identified metal that may be preferably added ranges from 0.01 a/opercent to about 5.0 a/o percent of the silver content.

For the convenience of the reader, the following are some combinationsof silver alloys, where the alloying elements are identified by theirperiodic table symbols, which may be preferably alloyed with silver:Ag+Zn, or Ag+Cd, or Ag+Li, or Ag+Al, or Ag+Ni, or Ag+Mn, or Ag+Ti, orAg+Zr, or Ag+Pd+Zn, or Ag+Pt+Zn, or Ag+Pd+Mn, or Ag+Pt+Mn, or Ag+Zn+Li,or Ag+Pt+Li, or Ag+Li+Mn, or Ag+Li+Al, or Ag+Ti+Zn, or Ag+Zr+Ni, orAg+Al+Ti, or Ag+Pd+Ti or Ag+Pt+Ti, or Ag+Ni+Al, or Ag+Mn+Ti, orAg+Zn+Zr, or Ag+Li+Zr, or Ag+Mn+Zn, or Ag+Mn+Cu, or Ag+Pd+Pt+Zn orAg+Pd+Zn+Mn, or Ag+Zn+Mn+Li, or Ag+Cd+Mn+Li, or Ag+Pt+Zn+Li, orAg+Al+Ni+Zn, or Ag+Al+Ni+Ti, or Ag+Zr+Ti+Cd, or Ag+Zr+Ni+Li, orAg+Zr+Ni+Al, or Ag+Pt+Al+Ni, or Ag+Pd+Zn+Al, or Ag+Zr+Zn+Ti, orAg+Ti+Ni+Al.

In another embodiment, silver can be alloyed additionally with indium,chromium, nickel, germanium, tin, antimony, gallium, silicon, boron,zirconium, molybdenum, magnesium, cobalt, bismuth, yttrium and scandiumor mixture of these elements. In relation to the amount of silver thatis present in the alloy systems, the amount of the above-identifiedelements that may be added ranges from about 0.01 a/o percent to about5.0 a/o percent of the silver content. But more preferably, the amountof alloying elements added to silver may ranges from about 0.1 a/opercent to about 3.0 a/o percent. This is further illustrated in TableII for an optical information storage medium as presented in FIG. 3. Allthe optical property symbols in Table II have the same meaning as inTable I.

TABLE II Balance of reflectivity of Layer 0 and Layer 1 of DVD-9 duallayer disc for various silver alloy Layer 0 and typical aluminum alloyLayer 1. Composition T₀ R₀ R₁ ^(′) R Ag—2.5% In 0.500 0.212 0.208 0.91Ag—1.2% Cr 0.535 0.243 0.238 0.94 Ag—0.7% Ge 0.515 0.220 0.220 0.92Ag—1.0% Sn 0.504 0.216 0.211 0.92 Ag—0.5% Sb 0.520 0.224 0.224 0.93Ag—3.0% Ga 0.475 0.195 ,0.187 0.86 Ag—1.5% Si 0.490 0.202 0.199 0.90Ag—1.2% B 0.513 0.247 0.218 0.92 Ag—0.8% Mo 0.515 0.220 0.218 0.92Ag—3.7% Mg 0.538 0.24 0.233 0.96 Ag—0.6% Bi 0.517 0.222 0.217 0.945Ag—0.9% Co 0.495 0.203 0.208 0.91 Ag—0.4% Y 0.511 0.217 0.214 0.91Ag—0.3% Sc 0.518 0.223 0.226 0.94

It is well understood that the compositions listed in table I or TableII can also be used as the high reflectivity layer or layer 1 in aprerecorded dual layer optical disc structure such as DVD-9, DVD-14 orDVD-18, or in a tri-layer optical disc structure as in FIG. 4 or thehigh reflectivity layer in SACD or in a recordable optical disc such asDVD-R, DVD+R or in a rewritable optical disc such as DVD-RAM, DVD+RW orDVD-RW or rewritable disc with play back laser wavelength at about 400nm or as the one illustrated in FIG. 5.

For the convenience of the reader, the following are some combination ofsilver alloys, where the alloying elements are identified by theirperiodic table symbols, which may be preferably alloyed with silver:Ag+In, or Ag+.Cr, or Ag+Ge, or Ag+Sn, or Ag+Sb, or Ag+Ga, or Ag+Si, orAg+B, or Ag+Mo, or Ag+In +Cr, or Ag+Cr+Ge, or Ag+Cr+Sn, or Ag+Cr+Sb, orAg+Cr+Si, or Ag+Si+In, or Ag+Si+Sb, or Ag+Si+B, or Ag+Si+Mo, orAg+Mo+In, or Ag+Mo+Sn, or Ag+Mo+B, or Ag+Mo+Sb, or Ag+Ge+B, or Ag+In+Cr+Ge, or Ag+Cr+Sn+Sb, or Ag+Ga+Si+Mo, or Ag+Cr+Si+Mo, or Ag+B+Mo+Cr,or Ag+In +Sb+B, or Ag+Cr+Si+B, Ag+Ga+Ge+Cr, or Ag+Si+Ge+Mo orAg+Sb+Si+B, or Ag+Cr+Si+In, or Ag+Si+Cr+Sn.

The optical properties of a few of the ternary silver alloys of theapplication are further illustrated in Table III wherein thereflectivity and transmission as layer zero thin film in the thicknessof about 8 to 12 nm in a DVD-9 dual layer disc construction are shown.The meaning of each symbol is the same as in Table I.

TABLE III Balance of reflectivity of Layer 0 and Layer 1 of DVD-9 duallayer disc for various ternary silver alloy layer 0 and typical aluminumalloy Layer 1. Composition T₀ R₀ R₁ ^(′) R Ag—1.2%Pd—1.4%Zn 0.54 0.2450.242 0.95 Ag—0.8%Cu—1.5%Mn 0.535 0.240 0.238 0.94 Ag—1.5%Al—1.0%Mn 0.500.213 0.208 0.91 Ag—1.0%Cu—0.3%Ti 0.50 0.210 0.207 0.90 Ag—1.2%Al—1.3%Zn0.53 0.224 0.233 0.93 Ag—1.0%Ce—0.7%Al 0.49 0.203 0.201 0.89Ag—1.2%Sb—0.3%Li 0.47 0.187 0.183 0.83 Ag—0.8%Cu—1.5%Mg 0.54 0.243 0.2360.96 Ag—1.0%Zn—0.4%Bi 0.53 0.237 0.229 0.94 Ag—2.5%Mg—0.7%Co 0.51 0.2210.225 0.90 Ag—2.0%Mg—0.2%Y 0.52 0.227 0.219 0.93 Ag—0.7%Zn—0.3%Sc 0.510.215 0.210 0.92

In still another embodiment, the sputtering target and the thin film onthe optical information storage medium is a silver alloy with acomparatively small addition of copper as an alloying element inconjunction with other alloying elements selected from the groupconsisting of aluminum, nickel, manganese, titanium, zirconium, indium,chromium, germanium, tin, antimony, gallium, silicon, boron, molybdenumand mixtures thereof. In this embodiment, the relationship between theamounts of silver and copper ranges from about 0.01 a/o percent to about5.0 a/o percent copper and from about 95.0 a/o percent to about 99.99a/o percent silver. But preferably from about 0.1 a/o percent to about3.0 a/o percent copper, and from about 97.0 a/o percent to about 99.9a/o percent silver. In relationship to the amount of silver that ispresent in the alloy system, the amount of the above-identified elementsthat may be added ranges from 0.01 a/o percent to about 5.0% of thesilver content. But more preferably, the amount of alloying elementsadded to silver may ranges from about 0.1 a/o percent to about 3.0 a/opercent. As data presented in Table I, II and III indicated, if theindividual alloy addition to silver is more than 5.0 a/o percent, thebalanced reflectivity between layer zero and layer one in the DVD-9 duallayer disc structure is likely to be lower than the DVD specification of18 percent, therefore not composition with utility.

In still another embodiment, the sputtering target and the thin film onthe optical information storage medium is a silver alloy with additionalloying elements selected form the group consisting of cobalt, bismuth,magnesium, yttrium, and scandium, and mixtures thereof. In thisembodiment, the relationship between the amounts of silver and the otheralloying elements ranges from about 0.01 a/o percent to about 5.0 a/opercent of the other alloying elements and from about 99.99 a/o percentsilver to about 95.0 a/o percent silver. In yet another embodiment theamounts of the other alloying elements ranges from about 0.1 a/o percentto about 3.0 a/o percent with the silver concentration from about 99.9a/o percent to about 97.0 a/o percent.

Still another embodiment, is a silver alloy with copper as a secondalloy element, the amount of copper in the alloy varying from about 0.01a/o percent to about 10.0 a/o percent can further alloyed with any ofthe following elements singly or in mixture such as samarium, neodymium,terbium, thallium, thulium, and ytterbium etc. of the rare earth familyin the amount form about 0.01 a/o percent to about 5.0 a/o percent ofthe amount of silver present.

In yet another embodiment a silver copper alloy is further alloyed withmagnesium, the amount of copper in the alloy varying from about 0.01 a/opercent to about 10.0 a/o percent, the amount of magnesium varying fromabout 0.01 to about 5.0 a/o percent of the amount of silver present. Butpreferably, the amount of magnesium ranges from about 0.1 a/o percent toabout 3.0 a/o percent of the amount of silver present.

In yet another embodiment a silver copper alloy is further alloyed withcobalt, the amount of copper in the alloy varying from about 0.01 a/opercent to about 10.0 a/o percent of the amount of silver present, andthe amount of cobalt varying from about 0.01 to about 5.0 a/o percent ofthe amount of silver present. But preferably, the amount of cobalt inthe silver copper cobalt alloy ranges from about 0.1 a/o percent toabout 3.0 a/o percent of the amount of silver present.

In still another embodiment a silver copper alloy is further alloyedwith an additional element selected from the group of additionalelements consisting of yttrium, bismuth, scandium and mixtures thereof.In this embodiment, the relationship between the amounts of silver, theamount of the additional element varying from about 0.01 a/o percent toabout 5.0 a/o percent of the amount of silver present. But preferably,the additional element ranges from about 0.1 a/o percent to about 3.0a/o percent of the amount of silver present.

In another embodiment silver is alloyed with a comparatively smallamount of zinc and magnesium. In this embodiment, the relationshipbetween the amounts of zinc silver and magnesium ranges from about 0.01a/o percent (atomic percent) to about 15 a/o percent zinc and from about85 a/o percent to about 99.99 a/o percent silver, the amount ofmagnesium ranges from about 0.01 a/o percent to about 5.0 a/o percent ofthe amount of silver present. But preferably the silver, zinc, magnesiumalloy comprises about 0.01 a/o percent to about 10.0 a/o percent zinc ofthe amount of silver present, and about 0.01 a/o percent to 5.0 a/opercent magnesium of the amount of silver present.

In another embodiment, silver is alloyed with a comparatively smallamount of zinc and cobalt. In this embodiment, the relationship betweenthe amounts of zinc silver and cobalt ranges from about 0.01 a/o percent(atomic percent) to about 15 a/o percent zinc and from about 80 a/opercent to about 99.99 a/o percent silver, the amount of cobalt rangesfrom about 0.01 a/o percent to about 5.0 a/o percent of the amount ofsilver present. In one embodiment the silver zinc cobalt alloy comprisesabout 0.01 a/o percent to about 10.0 a/o percent zinc, and about 0.01 toabout 5.0 a/o percent cobalt of the amount of silver present.

In still another embodiment a silver zinc alloy is further alloyed withan additional element selected from the group of additional elementsconsisting of yttrium, bismuth, scandium, and mixtures thereof. In thisembodiment, the relationship between the amounts of silver, the amountof the additional element varying from about 0.01 a/o percent to about5.0 a/o percent of the amount of silver present. But preferably, theadditional element ranges from about 0.1 a/o percent to about 3.0 a/opercent of the amount of silver present.

Having presented the preceding compositions for the thin film materials,it is important to recognize that both the manufacturing process of thesputtering target and the process to deposit the target material into athin film play important roles in determining the final properties ofthe film. To this end, a preferred method of making the sputteringtarget will now be described. In general, vacuum melting and casting ofthe alloys or melting and casting under protective atmosphere, arepreferred to minimize the introduction of other unwanted impurities.

Afterwards, the as-cast ingot should undergo a cold working process tobreak down the segregation and the non-uniform as-cast microstructure.One preferred method is cold forging or cold uniaxial compression withmore than 50 percent of size reduction, followed by annealing tore-crystallize the deformed material into fine equi-axed grain structurewith preferred texture of <1,1,0> orientation. This texture promotesdirectional sputtering in a sputtering apparatus so that more of theatoms from the sputtering target will be deposited onto the discsubstrates for, more efficient use of the target material.

Alternatively, a cold multi-directional rolling process of more than 50percent size reduction can be employed, followed by annealing to promotea random oriented microstructure in the target and finally by machiningto the final shape and size suitable for a given sputtering apparatus.This target with random crystal orientation will lead to a more randomejection of atoms from the target during sputtering and a more uniformthickness distribution in the disc substrate.

Depending on different discs' optical and other system requirements,either a cold forging or a cold multi-directional rolling process can beemployed in the target manufacturing process to optimize the optical andother performance requirements of the thin film for a given application.

The alloys of this invention can be deposited in the well-known mannersdescribed earlier, those being sputtering, thermal evaporation orphysical vapor deposition, and possibly electrolytic or electrolessplating processes. Depending on the method of application, the alloythin film's reflectivity could vary. Any, application method that addsimpurities to or changes the surface morphology of the thin film layeron the disc could conceivably lower the reflectivity of the layer. Butto the first order of approximation, the reflectivity of the thin filmlayer on the optical disc is primarily determined by the startingmaterial of the sputtering target, evaporation source material, or thepurity and composition of the electrolytic and electroless platingchemicals.

It should be understood that the alloys of this invention can be usedfor future generations of optical discs that use a reading laser of ashorter wavelength, for example, when the reading laser's wavelength isshorter than 650 nanometers.

It should also be understood that, if the reflective film is reduced toa thickness of approximately 5 to 20 nanometers, a semi-reflective filmlayer can be formed from the alloys of this invention provided that theyhave sufficient light transmittance for use in DVD dual-layerapplications.

EXAMPLES Example 1

An alloy composition of silver with approximately 1.2 atomic percentchromium and approximately 1.0 atomic percent zinc will have areflectivity of approximately 94 to 95 percent at the wavelength of 800nanometers and a reflectivity of approximately 93 to 94 percent at thewavelength of 650 nanometers and a reflectivity of approximately 86 to88 percent at the wavelength of 400 nanometers with the film thicknessat about 60 to 100 nanometers.

Example 2

A silver-rich alloy with 1.5 a/o percent of manganese, 0.8 a/o percentof copper will have a reflectivity of approximately 94 to 95 percent at650 nanometers wavelength. If the thickness of the thin film is reducedto the 8 to 12 nanometers range, the reflectivity will be reduced to the18 to 30 percent range applicable for DVD-9's semi-reflective layer.Adding a low concentration of deoxidizer such as lithium can furthersimplify the manufacturing process of the starting material of the thinfilm. As silver has a tendency to dissolve some oxygen in the solidstate which tends to lower the reflectivity of the alloy, the addedlithium will react with the oxygen and lessen the degree of oxygen'simpact to reflectivity. The desirable range of lithium is in theapproximate range of 0.01 percent to 5.0 atomic percent, with thepreferred range from about 0.1 to 1.0 a/o percent.

Example 3

A silver based alloy with about 0.5 a/o percent of nickel and about 0.5a/o percent of zinc will have a reflectivity of approximately 95 percentat the wavelength of about 650 nanometers at a thickness of 60 to 70nanometers and is suitable for any high reflectivity application in anoptical information storage medium.

Example 4

Another silver based alloy sputtering target with the composition ofabout 1.0 a/o percent manganese, 0.3 a/o percent titanium and thebalance silver is employed to produce the semi-reflective layer of theDVD-9 dual layer disc with the following procedure: On top of atransparent polycarbonate half disc of approximately 0.6 millimeterthickness and 12 centimeter in diameter with information pits injectionmolded from a suitable stamper, a semi-reflective thin film or layer“zero” of silver based alloy approximately 10 to 11 nanometers inthickness is deposited or coated onto the half disc using the sputteringtarget of the above-mentioned composition in a magnetron sputteringmachine. On top of another transparent polycarbonate half disc ofapproximately 0.6 millimeter thickness with information pits injectionmolded from another suitable stamper, a high reflectivity thin film orlayer “one” of and aluminum based alloy approximately 55 nanometers inthickness is deposited using a suitable aluminum sputtering target inanother sputtering machine. These two half discs are then spin-coatedwith suitable liquid organic resins separately, bonded together withlayer “zero” and layer “one” facing each other and the resin is curedwith ultraviolet light. The distance between the layer “zero” and thelayer “one” is kept at about 55+/−5 microns within the disc. Thereflectivity of the two information layers is measured from the sameside of the disc and found to be about the same at 21 percent for, the650 nanometers wavelength laser light. Electronic signal such as jitterand PI error are measured and found to be within the published DVDspecifications. Subsequently, an accelerated aging test at 80 degrees C.and 85 percent relative humidity for 4 days is conducted on the disc.Afterwards, the reflectivity and the electronic signals are measuredagain and no significant changes were observed as compared to the samemeasurements before the aging test.

Example 5

A silver alloy sputtering target with the composition in atomic percentof about 0.2 percent lithium, 1.0 percent manganese, 0.3 percentgermanium and the balance silver is employed to produced thesemi-reflective layer of the DVD-9 dual layer disc. The procedure usedto make the discs is the same as in example 4 above. The reflectivity ofthe two information layer in the finished disc is measured from the sameside of the disc and found to be about the same at 22.5 percent for the650 nanometers wavelength laser light. Electronic signals such as jitterand PI error are also measured and found to be within the published DVDspecifications. Subsequently, an accelerated aging test at 70 degrees C.and 50 percent relative humidity for 96 hours is conducted on the disc.Afterwards, the reflectivity and the electronic signals are measuredagain and no significant changes are observed as compared to the samemeasurements before the aging test.

It is understood that the same silver alloy thin film in this exampledeposited on the disc in the thickness range from about 30 to about 200nanometers range can serve the purpose of the high reflectivity layersuch as Layer “one” in DVD-9, or Layer “two” in a tri-layer optical discas in FIG. 4 or other high reflectivity application in a rewritableoptical disc such as DVD-RW, DVD-RAM in a general structure asillustrated in FIG. 5 at 650 nanometers wavelength or any other futureoptical information storage medium played back at around 400 nanometerswavelength.

Example 6

A silver based alloy sputtering target with the composition in a/o % ofapproximately 1.3% manganese, 0.7% aluminum, and the balance silver isused to produce the reflective layer of a DVD-R disc, another type ofrecordable disc according to FIG. 2 with the following procedure: On topof a transparent polycarbonate half disc of about 0.6 mm thickness and12 cm in diameter with pregrooves suitable for DVD-R injection moldedfrom a suitable stamper, a cyanine based recording dye is spin-coated onthe substrate, dried, and subsequently a reflective layer of silverbased alloy approximately 60 nm in thickness is deposited or coated onthe recording dye using the sputtering target of the above mentionedcomposition in a magnetron sputtering machine. Afterwards, this halfdisc is bonded to another 0.6 mm thickness half disc by a UV curedresin. Information is recorded onto the disc in a DVD-R recorder and thequality of the electronic signal is measured. Then the disc is subjectedto an accelerated aging test at 80 degrees C. and 85% RH for 96 hours.Afterwards, the reflectivity and the electronic signal is measured againand no significant changes are observed as compared to the samemeasurements before aging test.

Example 7

A process to make the sputtering target with the composition asindicated in example 6 will be described hereafter. Suitable charges ofsilver, manganese and aluminum are put into the crucible of a suitablevacuum induction furnace. The vacuum furnace is pumped down to vacuumpressure of approximately 1 milli-torr and then induction heating isused to heat the charge. While the charge is heating up and the outgassing is finished, the furnace can be back filled with argon gas to apressure of about 0.2 to 0.4 atmosphere. Casting of the liquid melt canbe accomplished at a temperature of approximately 10% above the meltingpoint of the charge. The graphite crucible holding the melt can beequipped with a graphite stopper at the bottom of the crucible. Pouringof the molten metal into individual molds of each sputtering target canbe accomplished by opening and closing of the graphite stopper andsynchronizing this action with mechanically bringing each mold intoposition just underneath the melting crucible so that the proper amountof melt can be poured and cast into each target mold by gravity.Afterwards, additional argon flow into the vacuum furnace can beintroduced to cool and quench the casting to lower temperature.Subsequently, a cold or warm multi-directional rolling process with morethan 50% thickness reduction can be used to break up any nonuniformcasting microstructure. Then final anneal is done at 550 to 600 degreesC. in a protective atmosphere for 15 to 30 minutes. After machining thetarget piece into the right shape and size, cleaning in detergent andproperly dried, the finished sputtering target is ready to be put into amagnetron sputtering apparatus to coat optical discs. The approximatesputtering parameters to make the semi-reflective layer of an ultra highdensity optical disc with playback laser wavelength at 400 nanometers asmentioned in example 9 are 1 kilowatt of sputtering power, 1 second ofsputtering time at an argon partial pressure of 1 to 3 mili-torr for adeposition rate of 10 nanometers per second with the target to discdistance of approximately 4 to 6 centimeters. The high reflectivitylayer can be made with about the same sputtering parameters as thesemi-reflective layer except the sputtering power needs to be increasedto 4 to 5 kilowatts to deposit the high reflectivity layer using thesame sputtering target and sputtering apparatus. Thus a 5 inch diameterultra high density read-only optical disc can be made in this mannerwith user storage capacity of about 12 to 15 giga bytes per side. A duallayer disc with the construction as shown in FIG. 3, can storeapproximately 24 to 30 giga bytes of information, enough for a fulllength motion picture in the high-definition digital television format.

Example 8

A silver alloy sputtering target having the composition in a/o %: Pd,1.2%, Zn, 1.4% and balance silver was used to produce a dual layeroptical information storage medium as depicted in FIG. 3. Thin filmabout 10 nanometers thickness of this silver alloy was deposited by amagnetron sputtering machine on a suitable polycarbonate substrate. Thefeasibility of using the same silver alloy thin film for both thereflective layer and the semi-reflective layer of a dual layer ultrahigh density read-only optical disc with a playback laser wavelength at400 nanomaters is investigated. As indicated in FIG. 3, the indices ofrefraction n of the transparent substrate 214, the semi-reflective layer216, the spacer layer 218 and the high reflectivity layer are 1.605,0.035, 1.52, 0.035 respectively. The extinction coefficient k for thesemi-reflective layer and the high reflectivity layer is 2.0.Calculation shows that with a thickness of 24 nm, the semi-reflectivelayer will have a reflectivity Roof 0.242 and a transmission T₀ of 0.600in the disc at 400 nm wavelength. With a thickness of 55 nm, the highreflectivity layer will have a reflectivity R₁ of 0.685. Thereflectivity of the high reflectivity layer measured from outside thedisc through the semi-reflective layer will be R₀═R₁T₀ ² or 0.247. Inother words, to the detector outside the disc, the reflectivity fromboth the semi-reflective layer and the high reflectivity layer will beapproximately the same. This fulfills one of the important requirementsof a dual layered optical information storage medium that thereflectivity from these 2 layers of information should be approximatelyequal and the relationship between the optical properties of these twolayers is R₀═R₁T₀ ².

Example 9

The same silver alloy in example 8 can also be used as the highreflectivity layer and the two semi-reflective layers in a tri-layeroptical information storage medium as depicted in FIG. 4 at 400 nmplayback laser wavelength. Calculations show that for a thickness of 16nm for the first semi-reflective layer 316, a thickness of 24 nm for thesecond semi-reflective layer 320 and a thickness of 50 nm for the highreflectivity layer 324 in FIG. 4, the reflectivity measured at thedetector 332 will be 0.132, 0.137, 0.131 respectively from the threelayers. And approximately the same reflectivity from all three layerscan be achieved. Thus balance of reflectivity from three informationlayers using the same silver alloy can be achieved and one sputteringmachine and one silver alloy sputtering target can be used tomanufacture all three layers of an ultra high density tri-layer opticalinformation storage medium with playback laser wavelength at 400 nm in aproduction environment. It will be obvious that the aluminum alloys canalso be used for the high reflectivity layer of this tri-layer medium

Example 10

A silver alloy sputtering target having the composition in a/o %: Au,2.6%; Pd, 1.1%; Pt, 0.3%; Cu, 0.4% and balance silver was used toproduce the high reflectivity layer in a rewritable phase change discstructure or DVD+RW as shown in FIG. 5. On the 0.6 mm thicknesspolycarbonate substrate with continuous spiral tracks of grooves andlands injection molded form a suitable stamper, successive layers ofZnO.SiO₂, Ag—In—Sb—Te, and ZnO.SiO₂ with suitable thickness are coatedon the substrate. Afterwards the sputtering target of the abovecomposition is used in a magnetron sputtering apparatus to deposit about150 nm thickness of the silver alloy film on top of the ZnO'SiO₂ film.Subsequently, the half disc is bonded with a suitable adhesive to theother 0.6 mm thickness half disc with the same construction as mentionedabove to form the complete disc. Repeated record and erase cycles areperformed in a suitable DVD+RW drive. The disc meets the performancerequirements imposed on the recording medium. The disc further goesthrough an accelerated environmental test at 80 degrees C., 85% relativehumidity for 10 days. Afterwards, the disc performance is checked again,no significant change in the disc property is observed as compared tothe disc performance before the environmental test.

Example 11

A silver alloy sputtering target having the composition in a/o %: Cu,1.0%; Ag, 99.0% was used to produce the highly reflective layer in arewritable phase change disc structure or “DVR” as shown in FIG. 6except that between the dielectric layer 520 and the highly reflectivelayer 522, there is an interface layer of SiC (not shown). Compared toExample 10, layers in the disc in this example are deposited in thereverse order. The transparent substrate 524 was made of polycarbonateand injection molded from a suitable stamper, then the silver alloyreflective layer was deposited on the transparent substrate using theabove-mentioned sputtering target in a magnetron sputtering apparatus.The dielectric layer 520 (preferably ZnO.SiO₂), the recording layer 518(preferably Ag—In—Sb—Te), another dielectric layer 516 (preferablyZnO.SiO₂) and the interface layer (preferably SiC) were then vacuumcoated in sequence. Lastly, the disc was coated by a covering layer ofUV cured resin 514 10 to 15 microns in thickness. The performance of thedisc was verified with a DVR type of player with 400 nm wavelength laserbeam recording and play back system. Repeated record and erase cycleswere conducted satisfactorily. Afterwards, the disc was furthersubjected to an accelerated environmental test condition of about 80degrees C. and 85% relative humidity for 4 days. The performance of thedisc was again checked and verified. No significant degradation of thedisc property was observed.

Example 12

A silver alloy sputtering target having a composition given in a/o % of:Cu, 1.0%; Ag, 99.0% was used to produce the highly reflective layer in arewritable phase change disc structure or “DVR” as shown in FIG. 6. Inthis DVR structure, between dielectric layer 520 and highly reflectivelayer 522, there is an interface layer of SIC (not shown). The layers inthis example are deposited in the reverse order from the order of layeraddition used in Example 10. The transparent substrate 524 was made ofpolycarbonate and injection molded from a suitable stamper, then thesilver alloy reflective layer was deposited on the transparent substrateusing the above-mentioned sputtering target in a magnetron sputteringapparatus. Dielectric layer 520 (preferably ZnO.SiO₂), recording layer518 (preferably Ag—In—Sb—Te), another dielectric layer 516 (preferablyZnO.SiO₂) and an interface layer (preferably SiC) were then vacuumcoated, in sequence. Finally, the disc was covered with a layer of UVcured resin 514, about 100 microns thick.

The performance of the disc is verified with a DVR type recording andplay back system using a 405 nm wavelength laser beam. Repeated recordand erase cycles are conducted satisfactorily. The disc is subjected toan accelerated environmental test at 80 degrees C. and 85% relativehumidity for 4 days. The performance of the disc is again checked andverified. No significant degradation of the disc's property is observed.

Example 13

A silver based alloy sputtering target with a composition in a/o % ofapproximately 2.2% copper, 0.5% zinc, and the balance silver is used toproduce the semi-reflective layer or L0 of another type of recordabledisc such as a DVD-R dual-layer disc or a DVD+R dual-layer disc as shownin FIG. 13 using the following procedure. An azo based recording dye isspin-coated on top of a transparent polycarbonate half disc about 0.6 mmthick and 12 cm in diameter with pregrooves suitable for DVD-Rdual-layer or DVD+R dual-layer injection molded by a suitable stamper,and, dried. Subsequently, a semi-reflective layer of silver based alloyapproximately 10 nm in thickness is deposited or coated on the recordingdye using the sputtering target with the aforementioned composition in amagnetron sputtering machine. Afterwards, this half disc is bonded tothe other 0.6 mm thickness half disc using a UV cured resin. The otherhalf disc contains 150 nm thickness of silver alloy sputtered fromanother sputtering target of the composition: 1.7 a/o % Cu, 1.0 a/o % Znand 97.3 a/o % Ag on the clear polycarbonate substrate and subsequentlycoated with another Azo based recording dye and dried by hot circulatingair. Information is recorded onto both layers of the disc in a DVD-Rdual-layer or DVD+R dual-layer recorder and the quality of theelectronic signal is measured. The disc is then subjected to anaccelerated aging test at 80 degrees C. and 85% RH for 2 days.Afterwards, the reflectivity and the electronic signals of the disc aremeasured again and no significant changes are observed as compared tothe same measurements before the aging test.

In view of the figures, description, and examples additional embodimentsinclude the following embodiments.

In one embodiment, an optical storage medium, comprising: a first layerhaving a pattern of features in at least one major surface; and a firstcoating adjacent the first layer, the first coating includes a firstmetal alloy; wherein the first metal alloy comprises:

silver; and at least one other element, selected from the groupcomprising copper, zinc, silicon, cadmium, tin, lithium, nickel, cobalt,indium, chromium, antimony, gallium, boron, molybdenum, zirconium,beryllium, germanium, aluminum, manganese, titanium, yttrium, scandium,cobalt, bismuth, and magnesium, wherein said other elements may bepresent from about 0.01 a/o percent to about 15.0 a/o percent of theamount of silver present. In another embodiment said other elements maybe present from present from about 0.01 a/o percent to about 10.0 a/opercent of the amount of silver present. In still another embodimentsaid other elements may be present from present from about 0.01 a/opercent to about 5.0 a/o percent of the amount of silver present. And instill another embodiment said other elements may be present from presentfrom about 0.01 a/o percent to about 3.0 a/o percent of the amount ofsilver present.

In another embodiment, the first coating of the optical storage mediummay directly contact the first metal layer of the medium.

In another embodiment, the medium may further comprise a second layerhaving a pattern of features in at least one major surface and a secondcoating adjacent to the second layer. The second layer may include adielectric material. Additionally, the medium may include a third layerhaving a pattern of features in at least one major surface, the thirdlayer including an optically recordable material and a fourth layerhaving a pattern of features in at least one major surface, the fourthlayer may include a dielectric material.

In another embodiment, an optical storage medium has a substrate with apattern of features in at least one major surface and a recording layeradjacent the feature pattern. A semi-reflective layer then residesadjacent the recording layer. The optical storage medium may also have asecond substrate with a pattern of features in at least one majorsurface, a second recording layer adjacent the feature pattern, and asecond reflective layer adjacent the recording layer. A space layer isthen located between the first and second substrates. In one embodimentat least one of the reflective or semi-reflective coatings are made of,for example, silver and copper wherein the relationship between theamounts of silver and copper is defined by Ag_(x)Cu_(t) where0.90<x<0.999 and 0.001<t<0.10.

Still another embodiment is an optical storage medium comprising a firstlayer having a pattern of features in at least one major surface and asemi-reflective layer adjacent to the first feature pattern. Thesemi-reflective layer or coating can be comprised of any of the metalalloys of the invention suitable for use in a semi-reflective layer andcompatible for use with a laser in the range of 405 nm. The storagemedium further includes a second layer having a pattern of features inat least one major surface and a highly reflective layer or coatingadjacent to the second pattern of features. In one embodiment the firstpattern of features includes a spiral groove.

Yet another embodiment provides an optical storage device including, inaddition to a first layer and second layer each having feature patterns,a fourth layer including an optically recordable material positionedbetween a third layer including a dielectric material and a fifth layerincluding a dielectric material. Optical recording layer 4 anddielectric layers 3 and 5 are positioned between the first layer and thesecond layer. In one embodiment the feature pattern in either, or both,the first and second layers comprise a spiral groove either with orwithout data pits.

In one embodiment, the recordable material in layer 4 is a phasechangeable material.

In still another embodiment, the recordable material in layer 4 ismagnetic optical recordable material.

In yet another embodiment, the recordable material in layer 4 is aoptically active dye.

In another embodiment, the optically recordable material is aphase-changeable material. The optically recordable material maycomprise a phase changeable materials selected from the group consistingof Ge—Sb—Te, As—In—Sb—Te, Cr—Ge—Sb—Te, As—Te—Ge, Te—Ge—Sn, Te—Ge—Sn—O,Te—Se, Sn—Te—Se, Te—Ge—Sn—Au, Ge—Sb—Te, Sb—Te—Se, In—Se—Tl, In Sb,In—Sb—Se, In—Se—Tl—Co, Bi—Ge, Bi—Ge—Sb, Bi—Ge—Te, and Si—Te—Sn. Theoptically recordable material may be a magneto-optic material selectedfor example from the group consisting of Tb—Fe—Co and Gd—Tb—Fe.

Another embodiment, the first metal alloy in a layer of an opticalrecording medium. The metal alloy may comprise, for example, copper,zinc, and silver wherein copper is present from about 0.01 a/o percentto about 10.0 a/o percent, zinc is present from about 0.01 a/o percentto 10.0 a/o, of the amount of silver present. In another embodiment thesilver copper alloy further comprises cobalt or magnesium, whereincobalt or magnesium are present from about 0.01 a/o to about 5.0 a/opercent of the amount of silver present

In another embodiment is a metal alloy in a layer of an opticalrecording medium, the alloy may comprise copper, titanium, and silver,wherein copper is present in about 0.01 a/o percent to about 10.0 a/opercent of the amount of silver present, and titanium is present fromabout 0.01 a/o percent to about 5.0 a/o percent of the amount of silverpresent in the alloy.

Another embodiment is a metal alloy in a layer of an optical recordingmedium may comprise silver; and at least one other metal selected fromthe group consisting of gold, rhodium, ruthenium, osmium, iridium,platinum, palladium, and mixtures thereof, wherein at least one of thesemetals is present from about 0.01 a/o percent to about 5.0 a/o percentof the amount of silver present.

In another embodiment, the metal alloy in a layer of an opticalrecording medium may comprise silver, copper, and silicon, whereincopper is present from about 0.01 a/o percent to about 10.0 a/o percentof the amount of silver present, and silicon is present from about 0.01a/o percent to about 5.0 a/o percent of the amount of silver present.

In another embodiment, the metal alloy in a layer of an opticalrecording medium may comprise silver, copper, and magnesium or cobalt,wherein copper is present from about 0.01 a/o percent to about 10.0 a/opercent of the amount of silver present, and magnesium or cobalt ispresent from about 0.01 a/o percent to about 5.0 a/o percent of theamount of silver present.

Still another embodiment, is an optical information recording medium,comprising: a first substrate having a pattern of features in at leastone major surface; a first recording layer adjacent the feature pattern;and a first reflective layer adjacent to the first recording layer. Thereflective layer includes a first metal alloy; wherein the first metalalloy comprises: silver; and at least one other element selected fromthe group consisting of copper, zinc, titanium, cadmium, lithium,nickel, cobalt, indium, aluminum, germanium, chromium, germanium, tin,beryllium, magnesium, manganese, antimony, gallium, silicon, boron,zirconium, molybdenum, and mixtures thereof, wherein said other elementsare present from 0.01 a/o percent to 10.0 a/o percent of the amount ofsilver present. In another embodiment, the other elements of theaforementioned metal alloy are present from about 0.1 a/o percent to 5.0a/o percent of the amount of silver present in the alloy.

In one embodiment, the first recording layer of an optical informationrecording medium may directly contact the first metal layer.

Another embodiment, is a metal alloy in an optical recording medium,wherein the metal alloy comprises silver, copper, and zinc whereincopper is present from about 0.01 a/o percent to 10.0 a/o percent of theamount of silver present, and zinc is present from about 0.01 a/opercent to 10.0 a/o percent of the amount of silver present.

Another embodiment, is a metal alloy in a layer of an optical recordingmedium comprised of silver and at least one element selected from thegroup consisting of gold, rhodium, ruthenium, osmium, iridium, platinum,palladium, and mixtures thereof, wherein the element is present fromabout 0.01 a/o percent to 5.0 a/o percent of the amount of silverpresent.

Yet another embodiment, is an optical storage medium, comprising: afirst substrate having a pattern of features in at least one majorsurface; a semi-reflective layer adjacent a feature pattern, thesemi-reflective layer including a metal alloy; the metal alloycomprising: silver; and copper; wherein the relationship between theamounts of silver and copper is defined by Ag_(x)Cu_(y), where0.90<x<0.999, 0.001<y<0.10; a second substrate having a pattern offeatures in at least one major surface; a high reflective layer adjacentthe feature pattern of the second substrate; and at least one spacerlayer, located between said first and second substrates.

The aforementioned medium may further include a second substrate havinga pattern of features in at least one major surface and a secondreflective layer adjacent the second substrate. The metal alloy may alsobe comprised of at least one additional element selected from the groupconsisting of silicon, cadmium, tin, lithium, nickel, cobalt, indium,chromium, antimony, gallium, boron, molybdenum, zirconium, beryllium,titanium, magnesium, wherein the elements are present from about 0.01a/o percent to 10.0 a/o percent of the amount of silver present.

In still another embodiment, the first metal alloy in an optical storagemedium with both reflective and semi-reflective layers, comprisingAg_(x)Cu_(y), where 0.90<x<0.999, 0.001<y<0.10, includes manganesepresent from about 0.01 a/o percent to about 7.5 a/o percent of theamount of silver present.

In still another embodiment, the metal alloy in an optical storagemedium with both reflective and semi-reflective layers, comprisingAg_(x)Cu_(y), where 0.90<x<0.999, 0.001<y<0.10, includes manganesepresent from about 0.01 a/o percent to about 5.0 a/o percent of theamount of silver present.

In still another embodiment, the metal alloy in an optical storagemedium with both reflective and semi-reflective layers, comprisingAg_(x)Cu_(y), where 0.90<x<0.999, 0.001<y<0.10, includes titaniumpresent from about 0.01 a/o percent to about 5.0 a/o percent of theamount of silver present.

In still another embodiment, the metal alloy in an optical storagemedium with both reflective and semi-reflective layers, comprisingAg_(x)Cu_(y), where 0.90<x<0.999, 0.001<y<0.10, and said alloy furtherincludes silicon present from about 0.01 a/o percent to about 5.0 a/opercent of the amount of silver present.

In another embodiment the semi-reflective layer of optical storagemedium includes a metal alloy comprising Ag_(x)Cu_(y), wherein0.95<x<0.999, 0.001<y<0.050.

In another embodiment, an optical storage medium has at least onesemi-reflective layer comprising a metal alloy including Ag_(x)Cu_(y),wherein 0.95<x<0.999, 0.001<y<0.050.

In another embodiment, the semi-reflective layer of an optical storagemedium directly contacts the first metal alloy of the medium.

In another embodiment, an optical information recording medium, mayfurther include a second substrate having a pattern of features in atleast one major surface and spacer layer located between the first andsecond substrates.

One embodiment, is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises silver and zinc alloy wherein the relationship between theamount of silver and the amount of zinc is defined by Ag_(x)Zn_(y),where 0.85<x<0.9999 and 0.0001<y<0.15.

Another embodiment, is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective comprisesa silver and aluminum alloy where the relationship between the amount ofsilver and the amount of aluminum is defined by Ag_(x)Al_(z), where0.95<x<0.9999 and 0.0001<z<0.05.

Still another embodiment is an optical storage medium with a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer comprises a silver and zinc and aluminum alloy where therelationship between the amount of silver and the amount of zinc and theamount of aluminum is defined by Ag_(x)Zn_(y)Al_(z), where 0.80<x<0.998and 0.001<y<0.15, and 0.001<z<0.05.

Yet another embodiment is an optical storage medium with a firstsubstrate having a pattern of features in at least one major surface anda first reflective layer adjacent the feature pattern. The reflectivelayer comprises a silver and manganese alloy where the relationshipbetween the amount of silver and manganese is defined by Ag_(x)Mn_(t),where 0.925<x<0.9999 and 0.0001<t<0.075.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises silver and germanium alloy wherein the relationship betweenthe amount of silver and the amount of germanium is defined byAg_(x)Ge_(q), where 0.97<x<0.9999 and 0.0001<q<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a silver, copper, and manganese alloy wherein the relationshipbetween the amount of silver and the amount of copper and the amount ofmanganese is defined by Ag_(x)Cu_(p)Mn_(t), where 0.825<x<0.9998 and0.0001<p<0.10, and 0.0001<t<0.075.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a silver and yttrium alloy wherein the relationship betweenthe amounts of silver and yttrium is defined by Ag_(x)Y_(w), where0.95<x<0.9999 and 0.0001<w<0.05. In another embodiment the amount ofyttrium in the silver yttrium alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a silver and scandium alloy wherein the relationship betweenthe amounts of silver and scandium is defined by Ag_(x)Sc_(w), where0.95<x<0.9999 and 0.0001<w<0.05. In another embodiment the amount ofscandium in the silver scandium alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a silver and bismuth alloy wherein the relationship betweenthe amounts of silver and bismuth is defined by Ag_(x)Bi_(w), where0.95<x<0.9999 and 0.0001<w<0.05. In another embodiment the amount ofbismuth in the silver bismuth alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a metal alloy including silver and copper further alloyed withat least one element A, element A selected from the group of elementscomprising yttrium, scandium, and bismuth wherein the relationshipbetween the amounts of silver, copper, and element A is defined byAg_(x) Cu_(z)A_(w), where 0.85<x<0.9998, 0.0001<z<0.10, and0.0001<w<0.05. In another embodiment the amount of element A in thesilver, copper, element A alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a metal alloy including silver, copper, and cobalt wherein therelationship between the amounts of silver, copper, and cobalt isdefined by Ag_(x)Cu_(z)Co_(w), where 0.85<x<0.9998, 0.0001<z<0.10, and0.0001<w<0.05. In another embodiment the amount of cobalt in the silver,copper, cobalt alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a metal alloy including silver, copper, and magnesium, whereinthe relationship between the amounts of silver, copper, and magnesium isdefined by Ag_(x)Cu_(z)Mg_(w), where 0.85<x<0.9998, 0.0001<z<0.10, and0.0001<w<0.05. In another embodiment the amount of magnesium in thesilver, copper, magnesium alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a metal alloy including silver, copper and cobalt, wherein therelationship between the amounts of silver, copper, and cobalt isdefined by Ag_(x)Cu_(z)Co_(w), where 0.85<x<0.9998, 0.0001<z<0.10, and0.0001<w<0.05. In another embodiment the amount of cobalt in the silver,copper, cobalt, alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a metal alloy including silver, zinc, and magnesium, whereinthe relationship between the amounts of silver, zinc, and magnesium isdefined by Ag_(x)Zn_(y)Mg_(w), where 0.80<x<0.9998, 0.0001<y<0.15, and0.0001<w<0.05. In another embodiment the amount of magnesium in thesilver, zinc, magnesium alloy is defined by 0.0001<w<0.03.

Another embodiment is an optical storage medium with a first substratehaving a pattern of features in at least one major surface and a firstreflective layer adjacent the feature pattern. The reflective layercomprises a metal alloy including silver, zinc, and cobalt, wherein therelationship between the amounts of silver, zinc, and cobalt is definedby Ag_(x)Zn_(y)Co_(w), where 0.80<x<0.9998, 0.0001<y<0.15, and0.0001<w<0.05. In another embodiment the amount of cobalt in the silver,zinc, cobalt alloy is defined by 0.0001<w<0.03.

In addition to the alloys uniquely disclosed and discussed herein foruse in optical data storage devices, specific metal alloys that may beused as high reflective layers, surfaces, or coatings as well asspecific metal alloys that may used as semi-reflective layers, surfaces,or coatings in optical data storage devices device can be found in U.S.Pat. Nos. 6,007,889; 6,280,811, 6,451,402, and 6,544,616 to Nee; as wellas in U.S. Publications: 2003-0138591; and 2003-0215598 by Nee, thedisclosures of which are hereby incorporated by reference.

The invention claimed is:
 1. An optical storage medium, comprising: a. afirst layer having a pattern of pits and lands in at least one majorsurface; b. a reflective layer conforming to the pits and lands of thefirst layer; c. a second layer having a pattern of pits and lands in atleast one major surface; and d. a semi-reflective layer, including ametal alloy comprising silver, magnesium, and copper, conforming to thepits and lands of the second layer; e. wherein the amount of copper thatis present ranges from about 0.01 a/o percent to about 10.0 a/o percent.2. The medium of claim 1, wherein the amount of magnesium that ispresent ranges from about 0.01 a/o percent to about 5.0 a/o percent ofthe silver content.
 3. The medium of claim 2, wherein the amount ofmagnesium that is present ranges from about 0.1 a/o percent to about 3.0a/o percent of the silver content.
 4. The medium of claim 1, wherein theamount of copper that is present ranges from about 0.01 a/o percent toabout 5.0 a/o percent.
 5. The medium of claim 4, wherein the amount ofcopper that is present ranges from about 0.1 a/o percent to about 3.0a/o percent.
 6. Apparatus for making an optical storage medium, theapparatus comprising, in combination: a. a first layer having a patternof pits and lands in at least one major surface; b. means for sputteringa reflective layer onto the pits and lands of the first layer; c. asecond layer having a pattern of pits and lands in at least one majorsurface; d. a target comprising a metal alloy; and e. means forsputtering a semi-reflective layer from the target onto the pits andlands of the second layer; f. wherein the metal alloy comprises silver,magnesium, and copper; and g. wherein the amount of copper that ispresent ranges from about 0.01 a/o percent to about 10.0 a/o percent. 7.The apparatus of claim 6, wherein the amount of magnesium that ispresent ranges from about 0.1 a/o percent to about 3.0 a/o percent ofthe silver content.
 8. The apparatus of claim 6, wherein the amount ofcopper that is present ranges from about 0.01 a/o percent to about 5.0a/o percent.
 9. The apparatus of claim 8, wherein the amount of copperthat is present ranges from about 0.1 a/o percent to about 3.0 a/opercent.